BIO 201 Study Guide - Fall 2018, Comprehensive Midterm Notes - Evolution, Natural Selection, Sperm
12 Oct 2018
School
Department
Course
Professor
BIO 201
MIDTERM EXAM
STUDY GUIDE
Fall 2018
September 13, 2017
Information, Exchange, and Storage: Genetics and Inheritance
A. Law of segregation - two members of gene pair will separate during gamete formation
B. Dominance - an organism, with alternate forms of a gene will express the form that is
dominant; heterozygous
C. Independent assortment - genes for different traits assort independently of one another in
the formation of gametes
a. 9:3:3:1 phenotypic ratio, self cross with yellow wrinkled
b. Cross with homozygous dominant and homo recessive for two traits - production
of hybrids for both traits in 9331 ratio
c. Mendel’s inference
d. More than one chromosome, each chromosome is inherited independently from
other chromosomes
e. Achieved by the way in which chromosomes orient themselves during cell
division
D. P generation - true breeding purple and white flowers, homozygous for that trait
E. F1 generation - everyone will be heterozygous
F. F2 - recovered the mask F1 form
a. 3:1 ratio in F2 generation
Mendel’s law of independent assortment is about statistical independence.
Each additional chromosome in the genome means that more chromosome orientations are
possible, resulting more gamete diversity.
Law of independent assortment
Number of chromosome orientations = 2 ^(number of chromosome pairs)
Recombination of homologous chromosomes adds even more gamete diversity than
chromosome orientation alone.
Recombination combined with independent assortment = a lot of genetic diversity +
mutations
Sex chromosomes
● In mammals
○ Two non-homologous chromosomes, X and Y
○ They were once homologous and some homologous regions remain
○ Autosomal chromosomes - the remaining chromosomes (22 pairs in humans)
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● X chromosome
○ Many many genes
○ Mothers can pass on either x to offspring
● Y chromosome
○ Few genes = related to sperm and testes production
○ Fathers only pass his Y to sons
Males can never be homozygous or heterozygous on the sex chromosomes. A
chromosome in a diploid organism is hemizygous when only one copy is present.
Males = hemizygous for sex chromosomes
Sex-linked inheritance - phenotypes more common in one sex than the other
Most sex-linked genes are on the X chromosome
Recessive alleles on the X chromosome can be hidden in females by a dominant allele
Recessive alleles on the X chromosome would be apparent in males
Both males and females can be carriers and can be affected - autosomal recessive inheritance
X-linked inheritance
Only females can be a carriers and usually males are affected. Females can be affected if they
have 2 copies of the mutated allele. Females can get an unaffected allele which masks the
recessive
Sex-linked inheritance
Mutations in genes on the x chromosome can cause phenotypes more common in males
Duchenne muscular dystrophy
Red-green color blindness
Hemophilia
Fragile x syndrome
Baldness
Sex-linked chromosomes in the fruit fly
● Thomas Hunt Morgan
● Crossed a normal female with a mutated X chromosome male
● 100% red-eyed males all XY hemizygotes
● 100% red eyed females, carriers for white eye allele
● Cross 2
○ F1 red eyed female with red eye wild type
○ 100% red eyed
○ 50% homozygotes
○ 50% heterozygotes
50% red eyed males
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Mendel"s law of independent assortment is about statistical independence. Each additional chromosome in the genome means that more chromosome orientations are possible, resulting more gamete diversity. Number of chromosome orientations = 2 ^(number of chromosome pairs) Recombination of homologous chromosomes adds even more gamete diversity than chromosome orientation alone. Recombination combined with independent assortment = a lot of genetic diversity + mutations. They were once homologous and some homologous regions remain. Autosomal chromosomes - the remaining chromosomes (22 pairs in humans) Mothers can pass on either x to offspring. Few genes = related to sperm and testes production. Fathers only pass his y to sons. Males can never be homozygous or heterozygous on the sex chromosomes. A chromosome in a diploid organism is hemizygous when only one copy is present. Sex-linked inheritance - phenotypes more common in one sex than the other. Most sex-linked genes are on the x chromosome.
