Chapter 6: Cytogenetics

Question 1

chromosome structure

Answer 1

a long arm (q) and short arm (p), joined by the centromere

Question 2

why are there telomeres on the ends of each chromosomal arm?

Answer 2

it prevents chromosomes from sticking together and it shortens after cell division due to aging

Question 3

what are the types of chromosomes?

Answer 3

• Chromosomes pair assigned numbers
• Chromosomes are identified by size, centromere location, and banding pattern

Question 4

Autosomes vs Sex chromosomes

Answer 4

Autosomes are chromosomes other than the sex ones (1-22) and it’s not involved in sex determination. Females have homologous sex chromosomes (XX) and males have non-homologous (XY). The X and Y differ in shape and size.

Question 5

How does the X and Y Chromosomes determine sex in humans?

Answer 5

Children receive an X from their mom, but either an X or Y chromosome from their dad

Question 6

The X chromosome vs Y chromosome

Answer 6

The X chromosome is much larger and contains more genes than the Y. The X contains genes needed by both sexes while the Y contains mostly genes necessary for male development.

Question 7

Sex Determining Region of Y

Answer 7

a single gene that is the primary determinant of maleness

Question 8

Chromosome Banding Pattern

Answer 8

The staining of chromosomes produce a distinctive chromosome-specific banding pattern. Also the overall shape helps identify the specific chromosome #

Question 9

Karyotype

Answer 9

Chromosomes are arranged in pairs according to size, banding pattern, and centromere location

Question 10

What does karyotypes reveal?

Answer 10

• Total # of chromosomes present
• sex of an individual
• presence or absence of individual chromosomes
• possibility of structural abnormalities

Question 11

Prenatal chromosomal analysis

Answer 11

analysis of fetal cells from maternal blood

Question 12

Euploid

Answer 12

The normal diploid (2n) and haploid (n) number of chromosomes in human cells

Question 13

Polyploidy

Answer 13

An increase in the # of chromosome sets

Question 14

Triploidy

Answer 14

• most common
• fatal within a month
• most common is 69, XYY; resulting from dispermy

Question 15

Aneuploidy

Answer 15

Changes in chromosome #s involving less than the duplication of a whole chromosome set
- Often the gain/loss of a single chromosome

Question 16

Trisomy 18

Answer 16

-47+18
-Parental age is a common risk factor
- lethal within 2-4 months of age

Question 17

What is the leading cause of childhood intellectual disability?

Answer 17

Trisomy 21: Down Syndrome (47, +21)

Question 18

What is the cause of autosomal aneuploidy?

Answer 18

Most often due to non disjunction during meiosis

Question 19

what is the difference between nondisjunction in meiosis?

Answer 19

in meiosis 1, its failure of homologous chromosomes to separate. in meiosis 2, it’s failure of sister chromatids to separate.

Question 20

How is maternal age a risk factor?

Answer 20

At age 40, a mother’s oocytes have been in meiosis for more than 40 years so the chance for intercellular factors to cause damage to oocytes increases.

Question 21

What is turner’s syndrome?

Answer 21

• 45, X (monosomy of x chromosome)
• only viable monosomy in humans
• result from nondisjunction

Question 22

Klinefelter syndrome

Answer 22

• 46, XXY
• both maternal and paternal age
  increased atypical characteristics

Question 23

XYY syndrome

Answer 23

-47, XYY

Question 24

Translocation

Answer 24

• two non homologous chromosomes exchange parts
• no info is lost, just shuffled around
• sometimes no effect and sometimes can cause cancer

Question 25

inversion

Answer 25

• section of chromosome is flipped and reinserted into the same chromosome