LEC 18

Question 1

X & Y Chromosomes DIFFERENCES

Answer 1

1. Size and shape
2. Centromere location
3. How they function in the body
4. Carry different genes which code for different proteins

Question 2

X & Y Chromosomes are not ____________ to each other

Answer 2

1. homologous

Question 3

X-Chromosome (5)

Answer 3

1. Has approx. 1000 genes to code for various proteins
2. Includes the genes needed to be “female”
3. Also codes for other traits and characteristics not specifically related to being female
4. Females have a pair of homologous X chromosomes (XX)
5. Have a “back-up” so if something is wrong with one, the other can still function normally

Question 4

Y-Chromosome (4)

Answer 4

1. Y-chromosome has only a few genes
2. Includes the genes needed to be “male” (development of male genitalia, sperm and testosterone production)
3. Males have a non-homologous pair of sex chromosomes (XY)
4. Don’t have a “backup copy” and therefore is a greater chance of inheriting diseases associated with mutations of the sex chromosomes

Question 5

Sex Linked Inheritance

Answer 5

Inheritance patterns that depend on genes located on sex chromosomes

Question 6

Sex Linked Inheritance Y-linked

Answer 6

1. gene found on the Y chromosome
2. Relatively few documented examples (Y-linked infertility) because sole purpose is to produce male traits in offspring

Question 7

Sex Linked Inheritance X-linked

Answer 7

1. gene found on the X chromosome
2. Many examples because it carries information not related to determining gender of offspring

Question 8

X-Linked Inheritance in FEMALES

Answer 8

1. behaves like inheritance of recessive autosomes traits with homologous pairs of genes
2. Individual needs two (2) of the affected genes for trait/disorder to be expressed

Question 9

X-Linked Inheritance in MALES

Answer 9

1. genotype & phenotype are determined solely by the X chromosome
2. Individual needs only one (1) affected gene (from mom) for trait/disorder to be expressed

Question 10

Hemophilia (3)

Answer 10

1. Best known example of X-linked inheritance
2. “bleeder’s disease”
3. Affected individuals lack a blood clotting factor

Question 11

X-Linked Inheritance: Males receive trait from their carrier _________

Answer 11

mothers

Question 12

X-Linked Inheritance: Females _________ affected but are often carriers. Carriers are ___________.

Answer 12

1. rarely
2. heterozygous

Question 13

X-Linked Inheritance: Affected fathers _________ pass the trait to their sons

Answer 13

cannot

Question 14

X-Linked Inheritance: Affected _____ will pass the affected gene to their daughters.
- Daughter will either become a ______ or have the disorder
- Depends on the _______ they receive from their ________

Answer 14

1. fathers
2. carrier
3. gene
4. mother

Question 15

Sex influenced traits

Answer 15

Some traits influenced by the sex of the individual

Question 16

Sex influenced traits : baldness

Question 17

Chromosome Abnormalities can happen during: (3)

Answer 17

DNA Replication
Mitosis
Meiosis

Question 18

In mitosis and meiosis, abnormalities can result in the daughter cells having the _______ number of chromosomes

Answer 18

wrong

Question 19

Several different mechanisms can alter the number of chromosomes in daughter cells: (3)

Answer 19

1. Nondisjunction
2. Deletions
3. Translocations

Question 20

Nondisjunction (2)

Answer 20

1. Failure of homologous chromosomes or sister chromatids to separate properly during cell division
2. Results in too many/not enough chromosomes in an autosome or gamete

Question 21

Mitosis Results of Nondisjunction (2)

Answer 21

1. Both sister chromatids go to one cell
2. Don’t see results of nondisjunction in mitosis as daughter cells usually die off

Question 22

Meiosis Results of Nondisjunction (4)

Answer 22

1. Homologous chromosomes/sister chromatids fail to separate resulting in too many copies in egg or sperm 2. More serious as the affected gametes have the potential to become an entire organism
2. Most are unlikely to survive and die in early embryonic development
3. Some cases result in live births

Question 23

Nondisjunction in Meiosis: Down Syndrome
AKA “Trisomy 21”

Answer 23

1. Three copies of chromosome #21 are present
2. Incidence arises with advancing age of mother
3. May also originate with father if both parents are over 35

Question 24

Jacob Syndrome Chromosome

Answer 24

XYY

Question 25

Jacob Syndrome Results (3)

Answer 25

1. Men
2. tall but mostly normal testosterone production & development.
3. May have increased risk of learning disabilities, ADHD, depression, anxiety and autism spectrum disorder.

Question 26

Klinefelter Syndrome Chromosome

Answer 26

XXY

Question 27

Klinefelter Syndrome Results (5)

Answer 27

1. Men
2. tall and infertile.
3. Small testes, produce low levels of testosterone.
   4, May have mild mental impairment
4. May also develop enlarged breasts due to extra X chromosome

Question 28

Trisomy-X or Triple X Syndrome Chromosome

Answer 28

XXX

Question 29

Trisomy-X or Triple X Syndrome Results (3)

Answer 29

1. Women
2. may be taller than normal but no unusual physical features.
3. May have increased risk of learning and intellectual disabilities

Question 30

Turner Syndrome Chromosome

Answer 30

XO

Question 31

Turner Syndrome Results (3)

Answer 31

1. Women – short stature with altered body form.
2. Many don’t undergo puberty and are infertile as ovaries don’t develop completely.
3. Heart defects may lead to shorter lifespan

Question 32

Deletions

Answer 32

1. Piece of chromosome breaks off and is lost
2. Lethal to eggs and sperm because they can’t do without chromosomes
3. Possible for live birth to occur (but rare)
   Cri-du-chat (cat cry)
   Results from a deletion of chromosome #5

Question 33

Translocations

Answer 33

1. Piece of chromosome breaks off and re-attaches to a new location
   Attaches either on same chromosome or on another one
2. Results in subtle changes in gene expression and function
3. Increased risk of cancers and chronic myelogenous leukemia

Question 34

Recessive Genetic Disorders Disease is expressed if:

Answer 34

Person inherits TWO defective alleles (one from each parent)

Question 35

Recessive Disease can be inherited but not _________ when _____ allele is received, making it more common in _______ population than dominant disease causing alleles.

Answer 35

1. expressed
2. one
3. general

Question 36

examples of recessive genetic disorders (3)

Answer 36

1. Phenylketonuria (PKU)
2. Tay Sach’s
3. Cystic Fibrosis

Question 37

Phenylketonuria (PKU)

Answer 37

1. Mutation of chromosome #1
2. Accumulation of phenylalanine due to a missing enzyme required to metabolize it
3. Phenylalanine is converted to phenylpyruvic acid instead (toxic at high concentrations)
4. Guthrie test (PKU test done at birth) is used to determine if child is affected with this disorder

Question 38

Tay-Sachs Disease

Answer 38

1. Chromosome #15 affected
2. Enzyme deficiency disease
3. Unable to metabolize a special lipid causing it to accumulate in the brain leading to cerebral degeneration
4. Very common in Ashkenazi Jewish population

Question 39

Cystic Fibrosis

Answer 39

1. Found on chromosome #7
2. Defective version of protein that normally aids in transportation of chloride across cell membrane of epithelial cells
3. Cells produce thick, sticky mucous that clogs the lungs and pancreas

Question 40

Dominant Genetic Disorders (3)

Answer 40

1. Follows same pattern of expression as other dominant traits
2. Only one allele is required for disease to occur
3. Are uncommon because they tend to eliminate themselves from the population

Question 41

Huntington Disease

Answer 41

1. Progressive nerve degeneration leading to physical and mental disability and death
2. No known cure and is known as a dominant-lethal allele
3. Genetic testing is available to determine if an individual has the dominant allele causing Huntington’s