mendel and heredity biology ch. 8 ms. haut. pre-mendelian theory of heredity blending...
TRANSCRIPT
![Page 1: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/1.jpg)
Mendel and Heredity
Biology
Ch. 8
Ms. Haut
![Page 2: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/2.jpg)
Pre-Mendelian Theory of Heredity
Blending Theory—hereditary material from each parent mixes in the offspring Individuals of a population should reach a
uniform appearance after many generations Once traits are blended, they can no longer be
separated out to appear in later generations
![Page 3: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/3.jpg)
Pre-Mendelian Theory of Heredity
Problems—inconsistent with observations: Individuals of a population don’t reach uniform
appearance Traits can skip generations
![Page 4: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/4.jpg)
Modern Theory of Heredity
Based on Gregor Mendel’s fundamental principles of heredity Parents pass on discrete inheritable factors
(genes) to their offspring These factors remain as separate factors from
one generation to the next
![Page 5: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/5.jpg)
Useful Genetic Vocabulary
Homozygous—having 2 identical alleles for a given trait (PP or pp)
Heterozygous—having 2 different alleles for a trait (Pp); ½ gametes carry one allele (P) and ½ gametes carry the other allele (p)
Phenotype—an organism’s expressed traits (purple or white flowers)
Genotype—an organism’s genetic makeup (PP, Pp, or pp)
![Page 6: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/6.jpg)
Mendel’s Discoveries
Developed true-breeding lines—populations that always produce offspring with the same traits as the parents when parents are self-fertilized
Counted his results and kept statistical notes on experimental crosses
![Page 7: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/7.jpg)
Crosses Tracking One Characteristic: Flower Color
![Page 8: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/8.jpg)
x
x
x
x
x
x
x
Ratio3.15:1
3.14:1
3.01:1
2.96:1
2.95:1
2.82:1
2.84:1
3:1
![Page 9: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/9.jpg)
PP(homozygous)
Pp(heterozygous)
Pp(heterozygous)
pp(homozygous)
1
2
1 White
3
1
Purple
Purple
Purple
Genotypic Ratio 1:2:1 Phenotypic Ratio 3:1
Genotype versus Phenotype
![Page 10: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/10.jpg)
The Testcross
The cross of any individual to a homozygous recessive parent
Used to determine if the individual is homozygous dominant or heterozygous
CAUTION:Must perform many, many crosses to be statistically significant
![Page 11: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/11.jpg)
Mendel’s Principles of Heredity
First Law of Genetics: Law of Segregation alternate forms of genes are responsible for variations in
inherited traits for each trait, an organism inherits 2 alleles, one from
each parent If 2 alleles differ, one is fully expressed (dominant
allele); the other is completely masked (recessive allele) 2 alleles for each trait segregate during gamete
production
![Page 12: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/12.jpg)
Mendel’s Principles of Heredity
Second Law of Genetics: Law of Independent Assortment During gamete formation, the segregation of the
alleles of one allelic pair is independent of the segregation of another allelic pair
Law discovered by following segregation of 2 genes
![Page 13: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/13.jpg)
![Page 14: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/14.jpg)
Dihybrid Cross
![Page 15: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/15.jpg)
Mendelian Inheritance Reflects Rules of Probability
Rules of Multiplication: The probability that independent events will occur simultaneously is the product of their individual probabilities.
![Page 16: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/16.jpg)
Question: In a Mendelian cross between pea plants that are heterozygous for flower color (Pp), what is the probability that the offspring will be homozygous recessive?
Answer: Probability that an egg from the F1 (Pp) will receive a p allele
= ½ Probability that a sperm from the F1 will receive a p allele = ½ Overall probability that 2 recessive alleles will unite at
fertilization: ½ x ½ = ¼
Mendelian Inheritance Reflects Rules of Probability
![Page 17: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/17.jpg)
Mendelian Inheritance Reflects Rules of Probability
Question: For a dihybrid cross, YyRr x YyRr, what is the probability of an F2 plant having the genotype YYRR?
Answer: Probability that an egg from a YyRr parent will receive the
Y and R alleles = ½ x ½ = ¼ Probability that a sperm from a YyRr parent will receive the
Y and R alleles = ½ x ½ = ¼ Overall probability of an F2 plant having the genotype
YYRR: ¼ x ¼ = 1/16
Works for Dihybrid Crosses:
![Page 18: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/18.jpg)
Mendelian Inheritance Reflects Rules of Probability
Rules of Addition: The probability of an event that can occur in two or more independent ways is the sum of the separate probabilities of the different ways.
![Page 19: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/19.jpg)
Mendelian Inheritance Reflects Rules of Probability
Question: In a Mendelian cross between pea plants that are heterozygous for flower color (Pp), what is the probability that the offspring will being a heterozygote?
Answer: There are 2 ways in which a heterozygote may be produced:
the dominant allele may be in the egg and the recessive allele in the sperm, or the dominant allele may be in the sperm and the recessive allele in the egg.
![Page 20: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/20.jpg)
Mendelian Inheritance Reflects Rules of Probability
Probability that the dominant allele will be in the egg with the recessive in the sperm is ½ x ½ = ¼
Probability that the dominant allele will be in the sperm with the recessive in the egg is ½ x ½ = ¼
Therefore, the overall probability that a heterozygote offspring will be produced is ¼ + ¼ = ½
![Page 21: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/21.jpg)
Pedigree Analysis
Analysis of existing populations Studies inheritance of genes in humans Useful when progeny data from several
generations is limited Useful when studying species with a long
generation time
![Page 22: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/22.jpg)
= female
= male
= affected individual
= mating
= offspring in birth order I and II are generations
I
II
Symbols:
= Identical twins
= Fraternal twins
![Page 23: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/23.jpg)
Dominant Pedigree:
I
II
III
For dominant traits:•Affected individuals have at least one affected parent•The phenotype generally appears every generation•2 unaffected parents only have unaffected offspring
![Page 24: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/24.jpg)
Recessive Pedigree:
I
II
III
For recessive traits:•Unaffected parents can have affected offspring•Affected progeny are both male and female
![Page 25: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/25.jpg)
Recessive Human Disorders
Sickle-cell anemia; autosomal recessive Caused by single amino acid substitution in
hemoglobin Abnormal hemoglobin packs together to form
rods creating crescent- shaped cells
Reduces amount of oxygen hemoglobin can carry
![Page 26: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/26.jpg)
Genetic Testing & Counseling
Genetic counselors can help determine probability of prospective parents passing on deleterious genes Genetic screening for various known diseases
alleles (gene markers)
![Page 27: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/27.jpg)
Genetic Testing & Counseling
Fetal testing
Amniocentesis
needle inserted into uterus and amniotic fluid extractedTest for certain chemicals or proteins in
the fluid that are diagnostic of certain diseases
Karyotype-can see chromosome abnormalities
![Page 28: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/28.jpg)
Genetic Testing & Counseling Fetal testing Chorion Villus Sampling
Suctions off a small amount of fetal tissue from the chorionic villus of placentaKaryotype-can see chromosome abnormalities
![Page 29: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/29.jpg)
Ultrasound at 12 weeks--can see any physical abnormalities
![Page 30: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/30.jpg)
Variations to Mendel’s First Law of Genetics
Incomplete dominance—pattern of inheritance in which one allele is not completely dominant over the other Heterozygote has a phenotype that is
intermediate between the phenotypes of the 2 homozygous dominant parent and homozygous recessive parent
![Page 31: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/31.jpg)
Incomplete Dominance in Snapdragon Color
Genotypic ratio:
Phenotypic ratio:
1 CRCR: 2 CRCW: 1 CWCW
1 red: 2 pink: 1 white
F2
![Page 32: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/32.jpg)
Variations to Mendel’s First Law of Genetics
Codominance—pattern of inheritance in which both alleles contribute to the phenotype of the heterozygote
![Page 33: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/33.jpg)
Multiple Alleles
Some genes may have more than just 2 alternate forms of a gene.
Example: ABO blood groups A and B refer to 2 genetically determined
polysaccharides (A and B antigens) which are found on the surface of red blood cells (different from MN blood groups) A and B are codominant; O is recessive to A and B
![Page 34: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/34.jpg)
Multiple Alleles for the ABO Blood Groups
3 alleles: IA, IB, i
![Page 35: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/35.jpg)
Polygenic Traits
Skin pigmentation in humans--3 genes with the dark-skin allele (A, B, C) contribute one “unit” of darkness to the phenotype.
These alleles are incompletely dominant over the other alleles (a, b, c)--An AABBCC person would be very dark; an aabbcc person would be very light--An AaBbCc person would have skin of an intermediate shade
![Page 36: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/36.jpg)
Discovery of Sex-Linkage
Thomas Hunt Morgan provided convincing evidence for Chromosomal Theory of Inheritance
Experiments with Drosophila revealed sex-linkage traits. Why Drosophila? Easily cultured Prolific breeders Short generation times Only 4 pairs of chromosomes, visible under microscope
![Page 37: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/37.jpg)
Chromosomal Basis of Sex Varies with Organism
Fruit flies (Drosophila), like Mammals use an X-Y system XX = female, XY = male Y chromosome has many fewer genes than X chromosome Y chromosome has SRY gene, determines testes development
![Page 38: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/38.jpg)
Sex-Linked Genes have Unique Patterns of Inheritance
For genes on X chromosomes, females have 2 copies of gene—can have 2 different alleles
For genes on X chromosomes, males have only one allele; the allele they express Males’ X comes from mom (dad contributes Y) Males are said to be hemizygous If allele is recessive, it will be expressed
Genes on X chromosome are said to be sex-linked Males are more likely to have disorders that are
inherited as sex-linked recessives
![Page 39: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/39.jpg)
Sex-Linked Recessive Trait
![Page 40: Mendel and Heredity Biology Ch. 8 Ms. Haut. Pre-Mendelian Theory of Heredity Blending Theory—hereditary material from each parent mixes in the offspring](https://reader036.vdocuments.us/reader036/viewer/2022062321/56649f2c5503460f94c47836/html5/thumbnails/40.jpg)
F1 Generation: All red eyes
F2 Generation: 3 red eyes: 1 white eyes But, the recessive trait—white eyes—was linked to sex.
•All females had red eyes•½ males had red eyes and ½ had white eyes
The gene responsible is located on the X chromosome