BIO 261 Quiz #1 on Sep 20 (tut notes)

In Figure 2-18, how does the 3:1 ratio in the bottom-left-hand grid differ from the 3:1 ratio obtained by Mendel?

Mendel’s Experiment is an autosomal gene inheritance model while Figure 2-18 is a sex-linked inheritance model.

In Figure 2-18, what progeny would you predict from a cross of a red F2 male from the first cross and a red F2 female from the second cross?

Cross: W⁺y x W⁺W

¾ red eyes, ¼ white eyes. All females have red eyes (X-linked gene)

Name the key function of mitosis

Conservation d’information génétique (creation of 2 identical daughter cells)

Name two key functions of meiosis

division/reduction of chromosomes and creation of gametes

In what ways does the second division of meiosis differ from mitosis?

Meiosis has crossing over of chromosomes and recombination of alleles (non-identical sister chromatids)

If children obtain half their genes from one parent and half from the other parent, why aren’t siblings identical?

The children receive a random mix of parental genomes because of the recombination of genomes (there are 2^23 possibilities)

Human cells normally have 46 chromosomes. How many nuclear DNA molecules (chromatids) are present during metaphase of mitosis?

92 Chromatids (2 molecules)

2n=46, 2 diploids

Human cells normally have 46 chromosomes. How many nuclear DNA molecules (chromatids) are present during metaphase I of meiosis ?

92 chromatids (4 molecules)

2n=46, 2 diploids

Human cells normally have 46 chromosomes. How many nuclear DNA molecules (chromatids) are present after telophase of mitosis?

92 Chromatids (2 molecules)

2n=46, 2 haploids

Human cells normally have 46 chromosomes. How many nuclear DNA molecules (chromatids) are present after telophase I of meiosis?

46 chromatids (2 molecules)

1 diploid

Human cells normally have 46 chromosomes. How many nuclear DNA molecules (chromatids) are present after telophase II of meiosis?

23 chromatids (1 molecule)

1 haploid

Four of the following events are part of both meiosis and mitosis, but only one is meiotic. Which one?

(1) Chromatid formation

(2) spindle formation

(3) chromosome condensation

(4) chromosome movement to poles

(5) chromosome pairing

Chromosome pairing

What is Mendel’s First law ?

Equal segregation of alleles

What is Mendel’s Second law ?

Independent assortment

What is Mendel’s third law ?

Law of Dominance

If you had a fruit fly (Drosophila melanogaster) that was of phenotype A, what cross would you make to determine if the fly’s genotype was A/A or A/a?

Test Cross with a/a individual resulting in a 1:1 genotypic ratio. If the fly is homozygous dominant, 0% of the progeny will have a recessive phenotype

Two black guinea pigs were mated and over several years produced 29 black and 9 white offspring. Explain these results, giving the genotypes of parents and progeny.

There is a 3:1 Ratio meaning both parents are heterozygous. ¼ of Offspring will be Homozygous Dominant. ½ will be Heterozygous. ¼ will be homozygous Recessive

The ability to taste is an autosomal dominant phenotype, and the inability to taste it is recessive. If a taster woman with a nontaster father meets a taster man who in a previous relationship had a nontaster daughter, what is the probability that their first child will be a NonTaster girl/Taster girl/Taster boy.

¼ x ½ = 1/8

¾ x ½ = 3/8

3/8

The ability to taste is an autosomal dominant phenotype, and the inability to taste it is recessive. If a taster woman with a nontaster father meets a taster man who in a previous relationship had a nontaster daughter. What is the probability that their first two children will be tasters of either sex?

¾ x ¾ = 9/16

John and Martha are contemplating having children, but John’s brother has galactosemia (an autosomal recessive disease) and Martha’s great-grandmother also had galactosemia. Martha has a sister who has three children, none of whom have galactosemia. What is the probability that John and Martha’s first child will have galactosemia?

¼

What is pedigree #1 ?

Recessive

What is pedigree #2 ?

Dominant

What is pedigree #3 ?

Dominant

What is pedigree #4 ?

Recessive

An X-linked dominant allele causes hypophosphatemia in humans. A man with hypophosphatemia marries a normal woman. If they have children, what proportion of their sons will have hypophosphatemia?

0%

Duchenne muscular dystrophy is sex linked and usually affects only males. Victims of the disease become progressively weaker, starting early in life.

What is the probability that a woman whose brother has Duchenne’s disease will have an affected child?

¼ x ½ = 1/8

Duchenne muscular dystrophy is sex linked and usually affects only males. Victims of the disease become progressively weaker, starting early in life.

If your mother’s brother (your uncle) had Duchenne’s disease, what is the probability that you have received the allele?

½

Duchenne muscular dystrophy is sex linked and usually affects only males. Victims of the disease become progressively weaker, starting early in life.

If your father’s brother had the disease, what is the probability that you have received the allele?

Girls have 100%. Boys have 0%