Chapter 7: Human Genetics

Question 1

Reasons why man is an unsuitable research subject (3)

Answer 1

a. Man has a long life cycle.
b. Man can not be made to interbreed randomly and can only bear a comparatively small number of progeny.
c. He can not be subjected to rigorous experimental conditions. ( i.e. Closely controlled matings and standardized experiments)

Question 2

Methods used to study human genetics (2)

Answer 2

• Pedigree Analysis
• Karyotyping

Question 3

• or family histories; Mode of transmission can be revealed
• to determine if the mode of inheritance is recessive, dominant, partial dominant, autosomal, mitochondrial or sex-linked. Moreover, it also determines the probability of an individual or offspring being affected in the given cross.

Answer 3

pedigree analysis

Question 4

• stained preparations of mitotic metaphase chromosomes are photographed, individual chromosomes are cut apart and arranged in pairs
• Through it, one can detect numerical and structural abnormalities.

Answer 4

Karyotyping

Question 5

Inheritance of traits can be observed in __.

Answer 5

families

Question 6

A pedigree indicates the structure of a __ schematically.

Answer 6

family

Question 7

Pedigrees give information on: (2)

Answer 7

• Dominance or recessiveness of alleles
• Risks (probabilities) of having affected offspring

Question 8

modes of transmission of hereditary traits

Answer 8

• autosomal dominance
• autosomal recessive
• sex-linked dominance
• sex-linked recessive

Question 9

• never skips a generation
• affected individuals may either be homozygous dominant or heterozygous for the trait.
• unaffected individuals are all homozygous recessive

Answer 9

autosomal dominance

Question 10

• Marriage between affected individuals produces offsprings who are also affected by the trait.
• Affected progenies may also result from mating between unaffected parents if they are heterozygous for the gene pair

Answer 10

autosomal recessive

Question 11

• CAN (but don’t have to) skip generations
• shaded individuals are homozygous recessive
• unshaded individuals that have shaded children must be heterozygous

Answer 11

autosomal recessive

Question 12

• Every affected person must have at least 1 affected parent
• Both males and females are affected and capable of transmitting the trait
• No skipping of generations
• No alternation of sexes: we see father to son, father to daughter, mother to son, and mother to daughter

Answer 12

autosomal dominant

Question 13

• Because most matings are with homozygous normal individuals and no offspring are affected
• Expect increased consanguinity between the parents.

Answer 13

autosomal recessive

Question 14

Autosomal disorders (2)

Answer 14

• Phenylketonuria
• cystic fibrosis

Question 15

• A hereditary disorder due to an autosomally recessive allele
• Most common disease in the U.S (1 in every 2000 births)
• Affected individuals die before reproductive age
• occur as a result of matings between heterozygotes.
• no homozygotes reproduce.

Answer 15

cystic fibrosis

Question 16

a hereditary disorder characterized by lung congestion and infection and malabsorption of nutrients by the pancreas

Answer 16

cystic fibrosis

Question 17

High frequency of carriers due to overcompensation; average number of children in families with CF child is 25% higher than in normal families (__ of normal children are carriers)

Answer 17

2/3

Question 18

CF gene was identified and sequenced in 1989; encodes a large protein (about 1500 aa) that functions in cell membranes to regulate __ __ inside cells.

Answer 18

water balance

Question 19

• Defective CF protein prevents __ __ from exiting cells, resulting in excess water inside the cell.
• All __-__ glands malfunction especially those in the __ and __ systems.

Answer 19

• chloride ions
• mucus-producing
• respiratory
• digestive

Question 20

Cystic Fibrosis
- Leads to the buildup of thick dry mucus in the __ causing persistent cough and breathing difficulty. Residual mucus also good medium for __ __(pneumonia and other infections)

Answer 20

• lungs
• bacterial growth

Question 21

Cystic fibrosis
* Mucus also clogs ducts of the __, blocking the passage of important enzymes; food can not be digested=malnutrition

Answer 21

• pancreas

Question 22

Cystic fibrosis
* unusually high concentration of __ in sweat (2-5 times); detected when parents kiss their babies
* Clinically detected using the __ __- measures concentration of __ in a sample taken from a warmed patch on the child’s back or forearm

Answer 22

• salt
• sweat test
• salt

Question 23

__ has no cure; therapeutic abortion the only way
* Possibly gene therapy

Answer 23

Cystic fibrosis

Question 24

• Act as recessive traits in females, but dominant traits in males
• An affected male cannot pass the trait on to his sons, but passes the allele on to all his daughters, who are unaffected carriers
• A carrier female passes the trait on to 1/2 her sons

Answer 24

X-linked Recessive Disorders

Question 25

X-linked Recessive Disorders * Act as recessive traits in __, but dominant traits in __ * An __ __ cannot pass the trait on to his sons, but passes the allele on to all his daughters, who are __ __ * A carrier female passes the trait on to __ her sons

Answer 25

- females - males - affected male - unaffected carriers - 1/2

Question 26

X-linked Recessive Disorders (4)

Answer 26

- Hemophilia A - fragile X syndrome - Duchenne muscular dystrophy - color blindness

Question 27

- X-linked recessive disorder that that causes physical abnormalities, behavioral issues and a wide range of other health problems, including: Developmental delays. Intellectual disabilities. Learning disabilities. Anxiety. - caused by changes in a gene called Fragile X Messenger Ribonucleoprotein 1 (FMR1).

Answer 27

Fragile x syndrome

Question 28

centromeres in the middle of the chromosome

Answer 28

metacentric

Question 29

with centromeres slightly offcenter

Answer 29

submetacentric

Question 30

have centromeres almost at the ends

Answer 30

acrocentric

Question 31

chromosomes have terminal centromeres.

Answer 31

telocentric

Question 32

type of disorder: 22II + I21+ XX or XY (2n=47) (extra copy of one of chromosome 21)

Answer 32

Down syndrome

Question 33

type of disorder: mental retardation, slanting eyes, Mongolian eyelid fold, saddle nose, swollen tongue

Answer 33

down syndrome

Question 34

type of disorder: harelip/cleft palate, serious cerebral, ocular and cardiovascular defect

Answer 34

Patau's syndrome

Question 35

type of disorder: 22II+ I13+ XX or XY (2n=47)

Answer 35

Patau’s Syndrome

Question 36

type of disorder: 22II+I18+XX or XY (extra copy of chromosome 18) (2n=47)

Answer 36

Edward's syndrome

Question 37

type of disorder: malformations in every organ system

Answer 37

Edward's syndrome

Question 38

type of disorder: 22II+ X0 (only has 1 normal X sex chromosome) (2n=45)

Answer 38

Turner's syndrome

Question 39

type of disorder: 22II+XXX (2n=47)

Answer 39

Metafemale

Question 40

type of disorder: 22II+XXY (2n=47)

Answer 40

Klinefelter’s syndrome

Question 41

type of disorder: 22II+XYY (2n=47)

Answer 41

Double Y syndrome

Question 42

type of disorder: sexual infantilism, mental retardation

Answer 42

Turner's syndrome

Question 43

type of disorder: mental retardation, premature, menopause

Answer 43

metafemale

Question 44

type of disorder: underdevelopment in males, sterility, mental retardation

Answer 44

Klinefelter's syndrome

Question 45

type of disorder: antisocialism, aggressiveness, criminal tendencies, low IQ

Answer 45

Double Y syndrome

Question 46

Inherited human traits (8)

Answer 46

- Widow’s Peak - Straight hairline - Hitchhiker's thumb - tongue rolling - bent little finger - cleft chin - attached earlobes - freckles

Question 47

__ ear lobes are inherited as a dominant trait.

Answer 47

Unattached

Question 48

__ ear lobes are inherited as a recessive trait.

Answer 48

Attached

Question 49

Hand-clasping right thumb over left is a __ trait

Answer 49

recessive

Question 50

Hand-clasping left thumb over right is a __ trait

Answer 50

dominant