Lecture 3 - Meiosis & Heredity (Part 1)

Question 1

If all that occurs is independent assortment, how many different genotypes outcomes are possible in a human gamete?

L3 S10

Answer 1

2^23 = 8.38 million

Question 2

What complications can occur from crossing over?

L3 S11-12

Answer 2

Crossing over can result in unequal exchange of genetic material; one chromosome can get two copies of a gene while the other gets no copies.

Question 3

How many daughter cells are produced from meiosis and how do they differ from the parent cell?

L3 S16

Answer 3

• four daughter cells are produced
• daughter cells are haploid instead of diploid
• they are genetically distinct from parent cell (due to crossing over, independent assortment, and reduced chromosome number)
• epigenetic modifications are removed and replaced with parent specific modifications

Question 4

Which of the following events takes place in meiosis II, but not in meiosis I?

L3 S17

A. Crossing over
B. Contraction of chromosomes
C. Separation of homologous chromosomes
D. Separation of chromatids

Answer 4

D. Separation of chromatids

Question 5

What is cohesin.

L3 S21

Answer 5

Protein complex that holds sister chromatids together during mitosis and meiosis.

Question 6

What is the primary difference between spermatogenesis and oogenesis.

L3 S24

Answer 6

Spermatogenesis:
-4 equally viable sperm are produced

Oogenesis:
-meiosis I produces a secondary oocyte and a first polar body (disintegrates) and meiosis II produces an ovum (functional gamete) and a second polar body (disintegrates)

Question 7

What is the the result of improper segregation of chromosomes during meiosis?

L3 S28

Answer 7

Aneuploidy, abnormal chromosome number.

Trisomy is when there are 3 copies of a chromosome.
Monosomy is when there is one copy of a chromosome.

Question 8

Differentiate between heredity and heritability.

L3 S30

Answer 8

Heredity:
-passing of physical or mental characteristics genetically from one generation to the next

Heritability:
-proportion of genetic variation between genetics in a population

Question 9

What is crossing over and what is it’s significance?

L3 S11

Answer 9

Exchange of genetic material between homologous chromosomes. Creates chromosomes with a new combination of genes which enhances genetic variation.

Question 10

What conclusions could be made from Gregor Mendel’s observation of monohybrid crosses? (4)

L3 S37

Answer 10

• a phenotype is encoded by two alleles
• the genetic factors separate when gametes are formed
• traits can be dominant or recessive
• the two alleles separate with equal probability

Question 11

What are independent assortment and the law of segregation?

L3 S40

Answer 11

Law of segregation:
-each gamete only receives one of each allele for a specific gene

Independent assortment:
-genes for separate traits are passed down independent of one another to offspring

Question 13

If an F1 plant (round seed, heterozygous) is backcrossed to the parent with round seeds (homozygous), what proportion of the progeny will have wrinkled seeds?

L3 S43

A. 3/4
B. 1/2
C. 1/4
D. 0

Answer 13

D. 0