mendelian genetics. genetics is everywhere these days and it will continue as a dominant force in...
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Gregory Mendel – Australian monk Afterwards became Father of modern genetics Researched with pea plants Developed ideas of dominance and trait segregationTRANSCRIPT
MENDELIAN GENETICS
Genetics is everywhere these days – and it will continue as a dominant force in biology and society for decades to come.
Gregory Mendel – 1822- 1884
•Australian monk
•Afterwards became Father of modern genetics
•Researched with pea plants
•Developed ideas of dominance and trait segregation
How Genetics Began The passing of traits to the next generation
is called inheritance, or heredity. Mendel performed cross-pollination in pea
plants. Mendel followed various traits in the pea
plants he bred.
MENDELIAN GENETICS
Mendel studied seven different traits. Seed or pea color Flower color Seed pod color Seed shape or texture Seed pod shape Stem length Flower position
MENDELIAN GENETICS
The second filial (F2) generation is the offspring from the F1 cross.
MENDELIAN GENETICS
Mendel crossed a pure yellow pea with a pure green pea
The offspring of this P cross are called the first filial (F1) generation.
Genes in Pairs
Allele
An alternative form of a single gene passed from generation to generation
They can be Dominant or Recessive
MENDELIAN GENETICS
DominanceAn organism with two of the same alleles for
a particular trait is homozygous.An organism with two different alleles for a
particular trait is heterozygous.
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Genotype and PhenotypeAn organism’s allele pairs are called its
genotype.The observable characteristic or outward
expression of an allele pair is called the phenotype.
An example of Genotype is Yy An example of Phenotype is yellow
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Mendel’s Law of Segregation Two alleles for each trait separate during meiosis. During fertilization, two alleles for that trait unite. Heterozygous organisms are called hybrids.
MENDELIAN GENETICS
Law of Independent Assortment Random distribution of alleles occurs during
gamete formation Genes on separate chromosomes sort
independently during meiosis. Each allele combination is equally likely to
occur.
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Genetic Recombination The new combination of genes produced by
crossing over and independent assortment
MENDELIAN GENETICS
Combinations of genes due to independent assortment can be calculated using the formula 2n, where n is the number of chromosome pairs.
Monohybrid Cross
A cross that involves hybrids for a single trait is called a monohybrid cross.
MENDELIAN GENETICS
Dihybrid Cross The simultaneous inheritance of two or more
traits in the same plant is a dihybrid cross. Dihybrids are heterozygous for both traits.
MENDELIAN GENETICS
Probability
• The likelihood that a particular event will occur• Example: What is the probability that a coin
when flipped will be heads? .. ½ X ½ = 50%
• What is the probability that a coin when flipped will be heads three times in a row?
½ X ½ X ½ = 1/8 or 1 out of 8 chance
MENDELIAN GENETICS
Punnett Squares
Predict the possible offspring of a cross between two known genotypes
Shows probability
Punnett Square—Dihybrid Cross
Four types of alleles from the male gametes and four types of alleles from the female gametes can be produced.
The resulting phenotypic ratio is 9:3:3:1.
Gene Linkage The linkage of genes on a chromosome results
in an exception to Mendel’s law of independent assortment because linked genes usually do not segregate independently.
Polyploidy Polyploidy is the occurrence of one or more extra
sets of all chromosomes in an organism.
A triploid organism, for instance, would be designated 3n, which means that it has three complete sets of chromosomes.
Complex Patterns of Inheritance
Incomplete Dominance The heterozygous phenotype is an
intermediate phenotype between the two homozygous phenotypes.
Codominance
Both alleles are expressed in the heterozygous condition.
Complex Patterns of Inheritance
Polygenic Traits Polygenic traits arise from the interaction of
multiple pairs of genes.
Complex Patterns of Inheritance
Multiple Alleles Blood groups in
humans ABO blood groups
have three forms of alleles.
Complex Patterns of Inheritance
Coat Color of Rabbits Multiple alleles can demonstrate a hierarchy
of dominance. In rabbits, four alleles code for coat color:
C, cch, ch, and c.
Complex Patterns of Inheritance
Coat Color of Rabbits
Light gray
Dark gray Himalayan
Albino
Chinchilla
Complex Patterns of Inheritance
Dosage Compensation The X chromosome carries a variety of
genes that are necessary for the development of both females and males.
The Y chromosome mainly has genes that relate to the development of male characteristics.
Complex Patterns of Inheritance
Sex Determination Sex chromosomes
determine an individual’s gender.
Complex Patterns of Inheritance
Sex-Linked Traits Genes located on the X chromosome
Red-green color blindness Hemophilia
Complex Patterns of Inheritance
Sex-Linked Traits
Environmental Influences Environmental factors Diet and exercise Sunlight and water Temperature
Complex Patterns of Inheritance
Pedigrees A diagram that traces the inheritance of a
particular trait through several generations
Karyotype—micrograph in which the pairs of homologous chromosomes are arranged in decreasing size.
Karyotype Studies
Images of chromosomes stained during metaphase
Chromosomes are arranged in decreasing size to produce a micrograph.
Cystic Fibrosis Affects the mucus-producing glands,
digestive enzymes, and sweat glands Chloride ions are not absorbed into the
cells of a person with cystic fibrosis but are excreted in the sweat.
Without sufficient chloride ions in the cells, a thick mucus is secreted.
Basic Patterns of Human Inheritance
Basic Patterns of Human Inheritance
Recessive Genetic Disorders
A recessive trait is expressed when the individual is homozygous recessive for the trait.
Albinism Caused by altered genes, resulting in the
absence of the skin pigment melanin in hair and eyes
White hair Very pale skin Pink pupils
Basic Patterns of Human Inheritance
Tay-Sachs Disease Caused by the absence of the enzymes
responsible for breaking down fatty acids called gangliosides
Gangliosides accumulate in the brain, inflating brain nerve cells and causing mental deterioration.
Basic Patterns of Human Inheritance
Dominant Genetic Disorders Huntington’s disease affects the nervous
system. Achondroplasia is a genetic condition that
causes small body size and limbs that are comparatively short.
Basic Patterns of Human Inheritance
Basic Patterns of Human Inheritance
Sickle-cell Disease Changes in hemoglobin
cause red blood cells to change to a sickle shape.
People who are heterozygous for the trait have both normal and sickle-shaped cells. Sickle cell
Normal red blood cell
7766x
Basic Patterns of Human Inheritance
1. A2. B3. C4. D
CDQ 1
A. #B. xC. rD. n
Which symbol is used to represent the number of chromosomes in a gamete?
Chapter Diagnostic Questions
1. A2. B3. C4. D
CDQ 2
Chapter Diagnostic Questions
A. Felix MendelssohnB. Gregor MendelC. Dr. Reginald PunnettD. Albert Einstein
Name the person known as the father of genetics.
1. A2. B3. C4. D
CDQ 3
Chapter Diagnostic Questions
A. gameteB. hybridC. phenotypeD. genotype
Which term refers to the outward expression of an allele pair?
1. A2. B3. C4. D
FQ 1
Segments of DNA that control the production of proteins are called _______.
A. chromatidsB. chromosomesC. genesD. traits
Formative Questions
1. A2. B3. C4. D
FQ 2
Formative Questions
What is the term for a pair of chromosomes that have the same length, same centromere position, and carry genes that control the same traits?
A. diploidB. heterozygousC. homozygousD. homologous
1. A2. B3. C4. D
FQ 3
Formative Questions
How does the number of chromosomes in gametes compare with the number of chromosomes in body cells?
A. Gametes have 1/4 the number of chromosomes.
B. Gametes have 1/2 the number of chromosomes.
C. Gametes have the same number of chromosomes.
D. Gametes have twice as many chromosomes.
1. A2. B3. C4. D
FQ 4
Formative Questions
What type of organisms only reproduce asexually?
A. bacteriaB. protistsC. plantsD. simple animals
1. A2. B3. C4. D
FQ 5
What is the name for different forms of a single gene that are passed from generationto generation?
A. allelesB. genotypesC. phenotypesD. traits
Formative Questions
1. A2. B3. C4. D
FQ 6
Formative Questions
Which pair of alleles is heterozygous?
A. RRB. RrC. rrD. yR
1. A2. B3. C4. D
FQ 7
Formative Questions
In rabbits, gray fur (G) is dominant to black fur (g). If a heterozygous male is crossed with a heterozygous female, what is the phenotypic ratio of the possible offspring?
A. 1:1B. 1:2:1C. 2:1D. 3:1
1. A2. B3. C4. D
FQ 10
Formative Questions
What is the term for an organism that has one or more sets of extra chromosomes in its cells?
A. diploid B. gameteC. hybridD. polyploid
1. A2. B3. C4. D
Standardized Test Practice
STP 4
To which step in this process does the law of segregation apply?
A. grows into plantB. gamete formationC. fertilizationD. seed development