Mitosis, Meiosis, Nondisjunction and Chromosome Rearrangements

Question 1

When does crossing over occur in meiosis?

Answer 1

During Prophase

Question 2

Which region is responsible for the recognition of homologous chromosomes in crossing over? Where is it found?

Answer 2

Pseudoautosomal Regions - near telomeres

Question 3

Does the Y Chromosome undergo recombination?

Answer 3

No

Question 4

True/False: chromosomes are randomly distributed in meiosis

Answer 4

True

Question 5

Is meiosis continuous or discontinuous in males and females?

Answer 5

Continuous in males

Discontinuous in females: beginning prophase I until puberty, Meiosis I takes place in one or a couple of oocytes each month

Question 6

How many mature gametes are produced in each round of meiosis per sex?

Answer 6

4 sperm

1 egg

Question 7

When can duplications and deletions occur in meiosis?

Answer 7

A section from one chromosome may move to another homolog during prophase I

Question 8

How do duplications/deletions alter a characteristic?

Answer 8

Genes encoded in the region can be expressed in proportion to their occurrences in the genome, and so one can suffer from an over or under expression of a specific gene or genes

Question 9

Can duplications be advantageous?

Answer 9

Yes, some populations have evolutionarily advantageous duplications which can lead to an increased production of advantageous proteins

Question 10

What are the 3 types of translocations?

Answer 10

1. Reciprocal
2. Nonreciprocal
3. Robertsonian

Question 11

Acute promyelocytic leukemia is an example of which kind of translocations?

Answer 11

Reciprocal translocations

Question 12

Down’s Syndrome can be due to the translocations of which two chromosomes?

Answer 12

14/21

Question 13

Inversions can often occur in attempts at ____ ______.

Answer 13

gene repair

Question 14

During recombination, chromosomes with inversions will form what?

Answer 14

Inversion loops

Question 15

___ _ Syndrome is a result of recombination with an inversion-containing chromosome.

Answer 15

Rec 8

Question 16

Nondisjunction describes what phenomenon?

Answer 16

The failure of homologous chromosomes to properly segregate

Question 17

Nondisjunction in MI will result in…

Answer 17

4 abnormal gametes

Question 18

Nondisjunction in MII will result in…

Answer 18

2 normal and 2 abnormal gametes

Question 19

Monosomy and trisomy are typically lethal/nonlethal?

Answer 19

Lethal

Question 20

Why is trisomy 21 likely to be less lethal to the zygote?

Answer 20

Chromosome 21 is the smallest autosome and thus causes less devastating gene damage to gene expression

Question 21

Imbalance in sex chromosomes in more or less damaging to the organism?

Answer 21

Less damaging

Question 22

How many X chromosomes are ever active?

Answer 22

1 X chromosome

Question 23

Inactive X chromosomes are…

Answer 23

Inactive and condensed into Barr Bodies

Question 24

The number of Barr Bodies can be used to identify what?

Answer 24

The number of supernumerary X chromosomes

Question 25

Sex Chromosome Aneuploidy are often seen as which two syndromes?

Answer 25

Turner’s and Klinefelter’s Syndromes

Question 26

What are the genotype bodies and symptoms of Turner’s Syndrome?

Answer 26

XO (2n-1)
45, X

Characteristic facial features, web of skin, constriction of aorta, poor breast development, and underdeveloped ovaries

Question 27

What are the genotype bodies and symptoms of Klinefelter’s Syndrome?

Answer 27

XXY (2n+1)
XXYY (2n+2)
XXXYY

Poor beard growth
Breast development
Underdeveloped testes

Question 28

Why is it thought that woman have increased risk of producing children with trisomy 21 as they age?

Answer 28

The proteins needed to maintain chromosomal integrity break down at the wrong time as women get older, namely [cohesin] and [shyoshin]

Question 29

Men over 40 y.o. are 6-times more likely to father children with ______ than men under 30 y.o. and are also more likely to produce children with _____________, ________, and generate miscarriages.

Answer 29

Autism, schizophrenia, dawrfism

Question 30

The body can recognize and attempt to rectify monosomies and trisomies, generating a ___________ ______.

Answer 30

Uniparental disomy

Question 31

Uniparental disomies can be problematic because…

Answer 31

Since the cell is no homozygous for that chromosome, genetic imprinting will go unrepressed.

Question 32

Which gene differs in humans from the rest of the great apes? What kind of variation is it?

Answer 32

A translocation on human Chr. 2