Ch 10

Question 1

What are homologous chromosomes?

Answer 1

• One chromosome of each pair comes from the mother and one from the father.
• Homologous chromosomes are similar but not identical. Each carry the same genre in the same order, but each trait is not the same.

Question 2

What are homologous pairs?

Answer 2

• a zygote contains 1 set of chromosomes from the ovum and 1 set from the sperm
• each set=a homologous pair of chromosomes

Question 3

What is a gamete? 2n or n?

Answer 3

Gametes= reproduction cells = 1n cells = ovum/sperm

Question 4

Are gametes diploid or haploid?

Answer 4

Haploid= 1n

Question 5

How many chromosomes do human gametes have?

Answer 5

diploid number of chromosomes is 46, the haploid number is half of this, or 23 chromosomes.

Question 6

If synapsids means joined, when are homologous chromosomes joined? Why is it called bivalent?

Answer 6

-when homologous chromosomes line up at the metaphase plate they are attached and align very closely.
Bivalent: there are two chromosomes

Question 7

During meiosis I what lines up at the metaphase plate?

Answer 7

-homologous chromosomes line up across from one another along the metaphase plate

Question 8

What is crossing over? During which phase of meiosis I does this occur?

Answer 8

• During meiosis, crossing over occurs during prophase I.
• It is the exchange of genetic material between homologous chromosomes that results in recombinant chromosomes, which contribute to genetic diversity.

Question 9

During what phase do homologous chromosomes separate?

Answer 9

-anaphase II

Question 10

When does interkinesis occur?

Answer 10

A short rest period to the second nuclear division occurring in meiosis II

Question 11

What chromosomes are in the nucleus of a cell during interkinesis?

Answer 11

• a short rest period prior to these end nuclear division occurring in meiosis II
• chromosomes still consist of two chromatids

Question 12

Are cells diploid or haploid during metaphase II?

Answer 12

-Haploid number of duplicated chromosomes at metaphase plate

Question 13

During what phase do sister chromatids separate in meiosis II?

Answer 13

Anaphase II

Question 14

How many daughter cells (gametes) are formed from one parent cell at the end of meiosis?

Answer 14

.During meiosis one cell divides twice to form four daughter cells. These four daughter cells only have half the number of chromosomes of the parent cell – they are haploid. Meiosis produces our sex cells or gametes

Question 15

What is the process of sperm formation and maturation called?

Answer 15

Spermatogenesis
-results in four cells that become sperm
Begins with primary spermatocytes
*has 46 chromosomes
-primary spermatocytes divides meiotically to form two secondary spermatocytes
*each set with 23 duplicated chromosomes
-secondary spermatocytes divide to produce four spermatids

Question 16

What is the process of egg formation called?

Answer 16

• oogenesis
• begins with primary oocytes
• has 46 chromosomes
• primary oocytes divided meiotically to form two secondary oocytes
• each with 23 duplicated chromosomes

Question 17

Define euploidy.

Answer 17

-correct number of chromosomes

Question 18

What is aneuploidy?

Answer 18

-changes to euploid: aneuploidy
-aneuploidy: monosomy and trisomy
*monosomy: an individual has only one of a particular type of chromosome
*trisomy: an individual has three of a particular type of chromosome
Due to nondisjunction

Question 19

How does nondisjunction result in aneuploidy?

Answer 19

• nondisjunction is the cause of abnormal chromosome numbers
• aneuploidy: monosomy and trisomy
• monosomy: an individual has only one of a particular type of chromosome
• trisomy: an individual has three of a particular type of chromosome

Question 20

What disorder is caused by nondisjunction of chromosome 21?

Answer 20

Down syndrome is usually caused by an error in cell division called “nondisjunction”

Question 21

How does nondisjunction result in a female with Turner syndrome?

Answer 21

• Genotype XO
• have only one sex chromosome
• affected individuals are sterile females
• ovaries never become functional
• do not undergo puberty
• are short, have a broad chest, folds of skin on the back of the neck
• otherwise normal

Question 22

How does nondisjunction result in a male with Klinefelter syndrome?

Answer 22

• genotype. XXY
• three sex chromosomes
• one Y chromosome and two or more X chromosomes
• Affected individuals are sterile males
• testes and prostrate are underdeveloped
• no facial hair

Question 23

What happens to a chromosome when there is a deletion?

Answer 23

• end of a chromosome breaks off

- —or two simultaneous breaks lead to the loss of internal segment

Question 24

Are there diseases caused by deletions?

Answer 24

• Williams syndrome

- Cri chat syndrome

Question 25

What happens to a chromosome when there is an inversion?

Answer 25

-inversion: a segment that has become separated from the chromosome in reinserted at the same place but in reverse.

Question 26

Does inversions cause disease?

Answer 26

- inversion has occurred when a segment of a chromosome has been turned around 180° - Most individuals with inversions exhibit no abnormalities, but this reversed sequence of genes can result in duplications or deletions being passed on to their children

Question 27

What happens to a chromosome when there is a translocation?

Answer 27

- segment is removed from one and inserted into another nonhomologous chromosome - translocation between chromosome 21 and 14 - duplication: a chromosomal segment occurs more that once in the same chromosome. - inversion: a segment that has become separated from the chromosome in reinserted at the same place but in reverse.

Question 28

Are there disease caused by translocations?

Answer 28

- Down syndrome - Alagille syndrome - certain types of cancer