chapter 12
DESCRIPTION
Chapter 12. Advanced Genetics. 11.3 Section Summary 6.3 – pages 296 - 301. Mutations. Mutation: a change in __. May involve : an entire __ a specific __ may take place in __ cell. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/1.jpg)
Chapter 12
Advanced Genetics
![Page 2: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/2.jpg)
Mutations
• Mutation: a change in __.– May involve :
• an entire __
• a specific __
– may take place in __ cell
• When a mutation takes place the DNA is changed which affects the production of __. This may affect metabolism, development, or result in a new phenotype.
![Page 3: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/3.jpg)
• Germ cell mutation - occurs in the __ cells.– This does not affect that organism but may be passed on
to the __.
Mutations in reproductive cells
• If this cell takes part in __, the altered gene would become part of the genetic makeup of the offspring.
![Page 4: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/4.jpg)
Mutations in reproductive cells result in:• A __ mutation - the embryo does not survive.
• A __ that does not work correctly.
• In some rare cases it may have a __ effect.
![Page 5: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/5.jpg)
• __ mutations - mutations in body cells– Ex)
• This mutation would __ be passed on to offspring.
Mutations in body cells
![Page 6: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/6.jpg)
Mutations in body cells result in:
• Impairing the __ of the cell.
• When that cell divides, the new cells also will have the same mutation.
• Affecting genes that control __.– Cells may grow and divide rapidly, producing __
![Page 7: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/7.jpg)
• A) __: a change in a single base pair in DNA. – A single nitrogen base is __ by another
• This may have __ noticeable affect or it can change the entire structure of a __ because a change in a single amino acid can affect the shape of the protein.
Types of Mutations
![Page 8: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/8.jpg)
The effects of point mutations
Normal
Point mutation
mRNA
Protein Stop
StopmRNA
Protein
Replace G with A
![Page 9: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/9.jpg)
• This mutation would cause nearly every __ in the protein after the __ to be changed.
• B) __: mutation in which a single base is added or deleted from DNA.
– Results in every __ after either the added or deleted base to be different.
![Page 10: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/10.jpg)
Frameshift mutations
mRNA
ProteinFrameshift mutation
Deletion of U
![Page 11: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/11.jpg)
• C) __: Structural changes in chromosomes. – Occur during __
– can be either changes in the __ of a chromosome or a __ of an entire chromosome.
– Are more __ types of mutations.
– __ are passed on to the next generation because the zygote usually dies.
– In cases where the zygote lives and develops, the mature organism is often __.
![Page 12: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/12.jpg)
• 1) Deletion- __.– It breaks off and all that information is now lost.
Deletion
A B C D E F G H A B C E F G H
Types of Chromosomal Alterations
![Page 13: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/13.jpg)
• 2) Duplication (__)- When part of a chromatid breaks off and attaches to its sister chromatid.
• The result is a duplication of genes on the __ chromosome.
Insertion
A B C D E F G H A B C B C D E F G H
Chromosomal Alterations
![Page 14: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/14.jpg)
• 3) Inversion- When part of a chromosome breaks off and __.
Inversion
A B C D E F G H A D C B E F G H
Chromosomal Alterations
![Page 15: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/15.jpg)
• 4) Translocation- When part of one chromosome breaks off and is added to __.
AB E FDCBXAWC HGGE HD F
WXY Z Y Z
Translocation
Chromosomal Alterations
![Page 16: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/16.jpg)
• How? – Errors in __ (mistake in base pairing)
– Errors in __
• 1) __ mutations: mutations that just seem to happen
Causes of Mutations
![Page 17: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/17.jpg)
• 2) __: Any agent that can cause a change in the __ (mutation)
• These are environmental factors such as:– a) __: such as X rays cosmic rays, ultraviolet light, and
nuclear radiation.– The energy they contain can damage or break apart __.
Causes of Mutations
![Page 18: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/18.jpg)
Causes of Mutations
– b) __ mutagens: include dioxins, asbestos, benzene, and formaldehyde.• Usually cause substitution mutations
– c) __
*__- Procedure used to identify mutagenic substances.
![Page 19: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/19.jpg)
Repairing DNA
• __ proofread the DNA and replace incorrect nucleotides with correct nucleotides.
• However, the __ the exposure to a mutagen such as UV light, the __ likely is the chance that a mistake will not be corrected.
![Page 20: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/20.jpg)
• Pedigree: a graphic representation of __ inheritance.
– Like a __.
• It is a diagram made up of a set of __ that identifies individuals affected by the trait being studied, and family relationships.
Pedigrees illustrate inheritancePedigrees illustrate inheritance
![Page 21: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/21.jpg)
Pedigrees illustrate
inheritance
Pedigrees illustrate
inheritance
Male
Female
Affected male
Affected female
Mating
Parents
Siblings
Known heterozygotes
for recessive allele
Death
![Page 22: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/22.jpg)
• In a pedigree, a __ represents a female; a __ represents a male.
Pedigrees illustrate inheritance
Pedigrees illustrate inheritance
Female Male
?
I
II
III
IV
1 2
1
1
1
32
2
2
4
3
3
5
4
4 5
![Page 23: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/23.jpg)
• Highlighted circles and squares represent individuals showing the trait being studied.
?
I
II
III
IV
1 2
1
1
1
32
2
2
4
3
3
5
4
4 5
Pedigrees illustrate inheritance
Pedigrees illustrate inheritance
![Page 24: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/24.jpg)
Pedigrees illustrate inheritance
Pedigrees illustrate inheritance
• Circles and squares that are not highlighted designate individuals that do not show the trait.
?
I
II
III
IV
1 2
1
1
1
32
2
2
4
3
3
5
4
4 5
![Page 25: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/25.jpg)
• A half-shaded circle or square represents a __: a heterozygous individual.
Pedigrees illustrate inheritancePedigrees illustrate inheritance
![Page 26: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/26.jpg)
1 2
1
1
1
32
2
2
4
3
3
5
4
4 5
?
I
II
III
IV
Pedigrees illustrate inheritancePedigrees illustrate inheritance• A horizontal line
connecting a circle and a square indicates that the individuals are parents (__ line), and a vertical line connects parents with their offspring (__ line).
![Page 27: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/27.jpg)
Pedigrees illustrate inheritancePedigrees illustrate inheritance• Each horizontal
row of circles and squares in a pedigree designates a __, with the most recent generation shown at the bottom.
1 2
1
1
1
32
2
2
4
3
3
5
4
4 5
?
I
II
III
IV
![Page 28: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/28.jpg)
1 2
1
1
1
32
2
2
4
3
3
5
4
4 5
?
Pedigrees illustrate inheritancePedigrees illustrate inheritance• The generations
are identified in sequence by __, and each individual is given an Arabic number.
I
II
III
IV
![Page 29: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/29.jpg)
• 1) __: an examination of a persons genetic makeup.
– This may involve:
• A) Blood test - looks for the presence or absence of certain __
Detecting Genetic Disorders
![Page 30: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/30.jpg)
• B) Karyotype- __.
– Procedure: remove __ from a cell
– stain and photograph chromosomes
– cut out each chromosome
– match it with its __
Detecting Genetic Disorders
![Page 31: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/31.jpg)
• 1) __- uses high-frequency sound waves to produce an image of a fetus on a moniter
– image is called a __
• 2) Amniocentesis- __.– Use a needle and syringe to remove some amniotic fluid.
– Make a __ and analyze.
Detecting Genetic Disorders: In a fetus
![Page 32: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/32.jpg)
• 3) Chorion villi sampling- analyze a sample of the chorion villi (tissue that grows between the __.)
– villi has the same __as the fetus.
• 4) __- a visual procedure for observing disorders in the fetus.
– Uses an instrument called an __
– can: observe fetus’ development, take skin and blood samples for analysis, do blood transfusions, and remove excess fluid from the brian.
Detecting Genetic Disorders: In a fetus
![Page 33: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/33.jpg)
Simple Recessive HereditySimple Recessive Heredity• Most genetic disorders are caused by __ alleles.
1) Cystic fibrosis1) Cystic fibrosis
• Due to a defective __ in the cell membrane.
• Results in the formation and accumulation of thick __ in the lungs and digestive tract.
• Common among __. (1 in 28 carries the allele, 1 in 2500 inherits the disorder)
• Average lifespan: __ yrs.
![Page 34: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/34.jpg)
2) Tay-Sachs disease2) Tay-Sachs disease
• Tay-Sachs (tay saks): a recessive disorder of the __.
• Results in the absence of an __ that normally breaks down a __ produced and stored in tissues of the central nervous system.
• Therefore, lipids accumulate in the cells.
![Page 35: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/35.jpg)
I
II
III
IV
Typical Pedigree
for
Typical Pedigree
for
1 2
1
1
1
32
2
4
3Tay-SachsTay-Sachs
![Page 36: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/36.jpg)
• Phenylketonuria (fen ul kee tun YOO ree uh): (PKU) the absence of an __ that converts one amino acid, phenylalanine, to a different amino acid, tyrosine.
• Phenylalanine and its by-products accumulate in the body resulting in severe damage to the __.
• A PKU test is normally performed on all __ a few days after birth.
• Infants affected by PKU are given a diet that is low in __ until their __ are fully developed.
3) Phenylketonuria3) Phenylketonuria
![Page 37: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/37.jpg)
• New Problem: If a female who is homozygous recessive for PKU becomes __, the high phenylalanine levels in her blood can damage her __ - the developing baby.
• This problem occurs even if the fetus is __ and would be phenotypically normal.
PhenylketonuriaPhenylketonuria
![Page 38: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/38.jpg)
PhenylketonuriaPhenylketonuria
Phenylketonurics: Contains Phenylalanine
![Page 39: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/39.jpg)
Simple Dominant HereditySimple Dominant Heredity
• A single dominant allele inherited from __ parent is all that is needed for a person to show the dominant trait.
![Page 40: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/40.jpg)
Simple dominant traits:Simple dominant traits:• 1) __
• 2) widow’s __
• 3) hitchhiker’s thumb
• 4) almond shaped __
• 5) thick lips
• 6) presence of __ on the middle section of you fingers
![Page 41: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/41.jpg)
Huntington’s diseaseHuntington’s disease• A __ genetic disorder
• Caused by a rare __ allele.
• Results in a breakdown of certain areas of the __.
• Symptoms: __ and irritability, eventually lose of __ control, uncontrollable physical __, severe mental illness, and eventually __.
![Page 42: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/42.jpg)
Huntington’s diseaseHuntington’s disease
• __: a short section of __ that indicates the presence of an allele that codes for a trait.
– __of people with this marker have a chance of developing HD
– can test before they have __.
• Usually occurs between the ages of __– An individual may already have had children
before knowing whether he or she is affected.
![Page 43: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/43.jpg)
Typical Pedigree of Huntington’s DiseaseTypical Pedigree of Huntington’s DiseaseI
1
II
III
2
1
1
3
2
2 4
3 4 5
5
![Page 44: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/44.jpg)
I
II
III
IV
1 2
1
1
1
32
2
4
3
Question 1 What does
this pedigree tell you about those who show the recessive phenotype for the disease?
![Page 45: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/45.jpg)
I
II
III
IV
1 2
1
1
1
32
2
4
3
The pedigree indicates that showing the recessive phenotype for the disease is __.
![Page 46: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/46.jpg)
• Thomas Hunt __ (early 1900’s) – Began a series of breeding experiments with Drosophila
melanogaster (__) Why use fruit flies?• Easy to maintain in a laboratory
• have a generation time of only __ days
• produce __ of offspring from each mating
• have easily distinguishable __ characteristics
• have only __ chromosomes
Genetic PatternsGenetic Patterns
![Page 47: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/47.jpg)
• He discovered that __ pair of chromosomes were different in males and females.
– In females: all pairs were __
– In males: the __ pair was different
• He called the large chromosome in the 4th pair the “__” chromosome and he called the short hooked one the “__” chromosome.
• The same applies to __.– Other organisms differ
Genetic PatternsGenetic Patterns
![Page 48: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/48.jpg)
• In humans the __ number of chromosomes is 46, or 23 pairs.
• __: A chromosome that is not a sex chromosome. There are __ pairs of homologous autosomes in humans. They all look alike.
• __ chromosomes: Chromosomes that determine an individual’s sex. They are the __ pair in humans and they differ in males and females.
Sex determinationSex determination
![Page 49: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/49.jpg)
Sex determinationSex determination• If you are __, your 23rd
pair of chromosomes are homologous, __.
• If you are __, your 23rd
pair of chromosomes __, look different.
X XFemale
YXMale
![Page 50: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/50.jpg)
• Males: Produce two kinds of __, X and Y.
• Females: Produce only __ gametes.
• It is the __ gamete that determines the sex of the offspring.
Sex determinationSex determination
![Page 51: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/51.jpg)
Sex determinationSex determination
XX Female
XY Male
X
X
X Y
XX Female
XY Male
XX Female
XY Male
![Page 52: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/52.jpg)
• __ hypothesized that some traits were always associated with one __ or the other.
– Ex) Most fruit flies have __ eyes • crossed a white-eyed male with a red-eyed female
• F1 - all had red eyes
• His hypothesis: The allele for eye color in fruit flies must be carried on the __ chromosome.
• Next he crossed the F1 generation
• expected a __ratio. He got it BUT…..
• Noticed all white-eyed flies were __. (in this example)
Sex-linked inheritanceSex-linked inheritance
![Page 53: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/53.jpg)
• Sex-linked traits: Traits controlled by genes located on the __.
• The alleles for sex-linked traits are written as __ of the X or Y chromosomes.
• The __ chromosome has no corresponding allele to one on the X chromosome and no __ is used. (Since X and Y are not homologous)
• Therefore, any __ allele on the X chromosome of a male will __ be masked by an allele on the Y chromosome.
Sex-linked inheritanceSex-linked inheritance
![Page 54: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/54.jpg)
Females:
Males:1/2 red eyed
1/2 white eyed
all red eyed
White-eyed male (XrY)
Red-eyed female (XRXR)
F1 All red eyed
F2
Sex-linked inheritanceSex-linked inheritance
![Page 55: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/55.jpg)
• Many human traits are determined by genes that are carried on the __; most of these genes are located on the __ chromosome. (Not the Y)
Sex-Linked Traits in Humans
• These traits are more common in __. WHY?– The __ chromosome does not carry a gene for these
traits so whatever allele is on the X chromosome is what trait will be expressed. (Dominant or recessive)
– Sons inherit these traits from their __ since that is who they are receiving the __ chromosome from.
![Page 56: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/56.jpg)
• Females, who are XX, pass one of their X chromosomes to __ child.
Sex-Linked Traits in Humans
Male Female
Sperm Eggs
FemaleFemale MaleMale
Female Male
MaleMaleFemale Female
Eggs Sperm
![Page 57: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/57.jpg)
• Caused by a __ allele
• These people can’t differentiate between red or green.
• __of males are color blind.
• Is __ in females.
Example: __color blindness
![Page 58: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/58.jpg)
• Hemophilia A: The __ does not clot properly because it lacks a __ essential for clotting.
Example: Hemophilia
• __: about one in every 10 000 has hemophilia. __: only about one in 100 million inherits it.
– Females would need __ recessive alleles to inherit hemophilia.
– Males inherit it from their carrier __. (One allele will cause the disorder in males.)
![Page 59: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/59.jpg)
• Polygenic inheritance: is the inheritance pattern of a trait that is controlled by __.
• Genes may be on the __ chromosome or on __ chromosomes. (Each gene may have two or more alleles.)
• All heterozygotes are __ in phenotype.– Phenotypes show a continuous range of variability.
– Ex) Plants: • aabbcc - 4cm tall
• AABBCC - 16cm tall
•
Polygenic inheritancePolygenic inheritance
![Page 60: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/60.jpg)
• Examples:– __
– __
– __
– __
Polygenic Inheritance in Humans
![Page 61: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/61.jpg)
• The __ genes, the __ ranges of skin color.
• Scientists found that when light-skinned people mate with dark-skinned people, their offspring have __ skin colors.
__: A polygenic trait
![Page 62: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/62.jpg)
• This graph shows the expected distribution of human skin color if controlled by one, three, or four genes.
Skin color: A polygenic trait
Number of Genes Involved in Skin Color
Observed distribution of skin color
Expected distribution- 1 gene
Expected distribution- 4 genes
Expected distribution- 3 genes
Range of skin color
Light Right
Nu
mb
er o
f in
div
idu
als
![Page 63: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/63.jpg)
Studying Human GeneticsStudying Human Genetics• Problem:
– May take __ years to produce 3 generations of humans.
– Each generation will produce only a __ individuals.
– Because of ethical __, scientists are prevented from using same procedures they would use on other organisms.
• Human inheritance patterns are very complicated. Their chromosomes contain atleast __ genes (7 times more than Drosopohila)
– SO……. How do scientists go about it?
![Page 64: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/64.jpg)
Studying Human GeneticsStudying Human Genetics• 1) Population sampling: __
– use carefully formulated statistical rules to select members of a sample to ensure they get accurate results.
– Ex) Used to estimate the percentage of people in the U.S. who could __ the chemical phenylthiocarbamide (PTC)
– “Tasters” - detect a bitter taste to PTC (65% of pop.)
– “Nontasters” do not detect any taste (35% of pop.)
![Page 65: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/65.jpg)
Studying Human GeneticsStudying Human Genetics• 2) __: Geneticists study __ twins to distinguish
between genetic and environmental influences on certain traits.
– Identical twins - have the same __ information. Differences may result from environmental influences (home life, education, etc…) Is more easily studied if raised by __ families.
• 3) __: Shows how traits have been passed down through the __.
![Page 66: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/66.jpg)
Environmental InfluencesEnvironmental Influences• The genetic makeup of an organism only determines
the organism’s __.
• As the organism develops, many factors can influence how the __ is expressed, or even if it is expressed at all.
• Two influences are:– 1) __ environment
– 2) __ environment
![Page 67: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/67.jpg)
• A)
• B)
• C)
• D)
• E)
Influence of external environmentInfluence of external environment
![Page 68: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/68.jpg)
Influence of external environmentInfluence of external environment
• In arctic foxes __ has an effect on the expression of coat color.
![Page 69: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/69.jpg)
• External influences can also be seen in leaves. Leaves can have different sizes, thicknesses, and shapes depending on the amount of __ they receive.
Influence of external environmentInfluence of external environment
![Page 70: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/70.jpg)
Influence of internal environmentInfluence of internal environment• A) __-influenced trait:
trait that is influenced by the presence of male or female sex __. Males and females have different hormones therefore __ are expresses differently.
– Ex) __ pattern baldness• __ in males
• __ in females
• B) __ can also affect gene function.
![Page 71: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/71.jpg)
• Both alleles are __ expressed in the heterozygous offspring.
__ in Humans
• Example: Sickle-cell disease (Sickle-cell anemia)
![Page 72: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/72.jpg)
• A - dominant allele, produces normal __
• A` - codominant allele, produces abnormal hemoglobin. (affects ability to carry __)
• AA` - have both __ and __ hemoglobin
Sickle-cell disease
– The defective hemoglobin changes the shape of the __. • Normal red blood cells are __-shaped
• Abnormal red blood cells are shaped like a __, or half-moon.
![Page 73: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/73.jpg)
• The change in shape occurs in the body’s narrow __ after the hemoglobin delivers oxygen to the cells.
Sickle-cell disease
Normal red blood cell
Sickle cell
![Page 74: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/74.jpg)
Sickle-cell disease• Results in : 1) Impairing the flow of __ 2) Slows __
flow, 3) __ clots, 4) Tissue damage and __ 5) __, 6) __, 7) Eventually failure of vital __.
Normal red blood cell
Sickle cell
![Page 75: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/75.jpg)
• Affects mainly __ population.– In U.S. __ of Black population carry the sickle-cell allele
– In Africa as many as __ carry it.
Sickle-cell disease
• Advantage to being a carrier:
• The parasite responsible for __ cannot survive in sickle cells, therefore, they are more likely to survive malaria.
![Page 76: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/76.jpg)
• Cause by a __ allele. Huntington’s Disease (HD)
• Symptoms: Forgetfulness, irritability first. Eventually loss of muscle control, uncontrollable physical spasms, severe mental illness, eventually death.
• Problem: Carriers do not know they have the disease until after they’ve had __.
• __: a short section of __ that indicates the presence of an allele that codes for a trait.
– Ex) __of people with this marker develop HD
![Page 77: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/77.jpg)
• __: when a replicated chromosome pair fails to separate during cell division.
Changes in Chromosome Numbers
• One daughter cell receives an __ chromosome and the other daughter cell __ a chromosome.
![Page 78: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/78.jpg)
• Trisomoy: Cells that have an __ autosome (they have __ of a particular chromosome instead of two.)
– Results in __ chromosomes
Abnormal numbers of autosomes
• Monosomy: Cells that are __ an autosome. (they have __ of a particular chromosome instead of two.)
– Results in __ chromosomes
![Page 79: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/79.jpg)
• Results from trisomy of chromosome __.
__ syndrome: Trisomy 21
• Individuals who have Down syndrome have at least some degree of __ retardation, folds of skin above the __, weak __, enlarged tongue, a rounder, fuller face, and are __ in height.
• The incidence of Down syndrome births is higher in older mothers, especially those over __.
![Page 80: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/80.jpg)
• Down syndrome is the __ autosomal trisomy in which affected individuals __ to adulthood.
Down syndrome: Trisomy 21
• It occurs in about one in __ live births.
![Page 81: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/81.jpg)
• Klinefelters Syndrome: – caused by __
– results in a __ of XXY
– is a __ with mental retardation, and low fertility
– occurs 1:1000 births
Abnormal numbers of sex chromosomes
• __ Syndrome: – caused by nondisjunction
– results in a __ of XO
– is a __ with immature physical development, sterility, and webbed neck.
– Occurs 1: 10,000 births
![Page 82: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/82.jpg)
• Genome: __.
• Human __ Project (HGP): organized by scientists in the United States in __.
– It is an international effort to completely __ and sequence the approximately 35,000-40,000 __ on the 46 human chromosomes. (human genome)
Mapping and Sequencing the Human Genome
![Page 83: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/83.jpg)
• In February of 2001, the HGP published its working draft of the __ base pairs of __ in most human cells.
Mapping and Sequencing the Human Genome
![Page 84: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/84.jpg)
• Improved techniques for prenatal diagnosis of human __, use of __ therapy, and development of new methods of __ detection are areas currently being researched.
Applications of the Human Genome Project
![Page 85: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/85.jpg)
• Linkage map (__): Shows the relative locations of __ on a chromosome.
– These genes are usually __ together
– Exception: __
Linkage maps
• These maps are made by studying the __data
![Page 86: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/86.jpg)
• Example using Drosophila– wing shape/eye color: linked 90% of the time, crossed
over __ of the time.
– Wing shape/body color: linked 93% of the time, crossed over __ of the time.
– Eye color/ body color: linked 83% of the time, crossed over __ of the time.
Linkage maps
• This information is used to create a linkage map. (Atleast __ traits must be compared)
![Page 87: Chapter 12](https://reader035.vdocuments.us/reader035/viewer/2022062517/56813034550346895d95cb19/html5/thumbnails/87.jpg)
• __: A unit in chromosome mapping equal to a __ occurrence of crossing over.
Linkage maps
• Example: If wing shape and eye color cross over 10 % of the time then they are __ map units apart.