Biology 1 Chapter 14 (Lecture)

Question 1

Gene

Answer 1

A heritable unit that determines a character; can exist in different forms.

Question 2

Allele

Answer 2

An alternative version of a gene

Question 3

Character

Answer 3

A heritable feature that varies among individuals

Question 4

Trait

Answer 4

A variant for a character

Question 5

Dominant Allele

Answer 5

Determines phenotype in a heterozygote

Question 6

Recessive Allele

Answer 6

Has no effect on phenotype in a heterozygote

Question 7

Genotype

Answer 7

The genetic makeup of an individual

Question 8

Phenotype

Answer 8

An organism’s appearance or observable traits

Question 9

Homozygous

Answer 9

Having two identical alleles for a gene

Question 10

Heterozygous

Answer 10

Having two different alleles for a gene

Question 11

Testcross

Answer 11

A cross between an idividual with an unknown genotype and a homozygous recessive individual

Question 12

Monohybrid Cross

Answer 12

A cross between individuals heterozygous for a single character

Question 13

Complete Dominance

Answer 13

Phenotypes of heterozygote and dominant homozygote are indistinguishable

Question 14

Incomplete Dominance

Answer 14

Phenotypes of heterozygotes is intermediate between the two phenotypes of both homozygotes

Question 15

Codominance

Answer 15

Two alleles each affect the phenotype in separate distinguishable ways

Question 16

Wild Type

Answer 16

Phenotype most commonly observed in the natural population

Question 17

Sex-Linked Gene

Answer 17

A gene located on sex chromosomes (x or y); usually occurs on x chromosome; fathers transmit this and other x-linked alleles to all daughters but not to sons. Any male who inherits such an allele from his mother will express the trait. (Thus, more males than females have x-linked recessive disorders)

Question 18

Genetic Recombination

Answer 18

Production of offspring with combination of traits that differ from those found in either parent

Question 19

Crossing Over

Answer 19

Reciprocal exchange of genetic material between nonsister chromatids during prophase I of Meiosis

Question 20

Nondisjunction

Answer 20

An error in meiosis or mitosis in which memebers of a pair of homologous chromosomes or a pair of sister chromatids fail to separate properly from each other.

Question 21

Cystic Fibrosis

Answer 21

• Most common lethal genetic disease in US
• Normal allele for this gene codes for chloride transport channels
• C. f. allele is recessive
• If homozygous for cf allele then high concentration of extracellular chloride which causes mucus buildup in organs
• If untreated most die before 5th birthday; in US half with cf survive to 20’ or 30’s

Question 22

Sickle-Cell Disease

Answer 22

• Most common inherited disorder among people of African descent
• Caused by substitution of single amino acid in hemoglobin protein
• Person homozygous all RBC are sickel shaped: can cause cells to clump and block blood vessels
• Regular blood transfusion and new drugs can help or prevent other problems it causes, but no cure
• Codominant at molecular level
• Sickle Cell Disease: both alleles are sickel cell alleles
• Sickel Cell Trait: One allele normal; one sickle cell
• Heterozygous advantage

Question 23

Huntington’s Disease

Answer 23

• Degenerative disease of the nervous system
• Irreversible & inevitably fatal
• Lethal dominant allele no obvious phenotypic effect until individual is 35 to 45 years old
• Child born to parent with Huntington’s Disease allel has 50% chance of inheriting the allel and the disorder
• Can do genetic testing to see if an individual has huntington’s allele in genome.

Question 24

Muscular Dystrophy

Answer 24

• Affects 1/3500 males born in US
• Progressive weakening of the muscles and loss of coordination
• Rarely live past early 20s
• X-linked disorder

Question 25

Hemophilia

Answer 25

* X-linked recessive disorder * Absence of one or more of proteins required for blood clotting * Treatment with IV injections of the protein that is missing

Question 26

Down's Syndrome

Answer 26

* Usually result of extra chromsome 21- each body cell has total of 47 chromosomes * Also called trisomy 21 * Characteristic facial features, short stature, developmental delays * Increases chance of developing many diseases * Have life span shorter than normal * Frequency increases with age of mother * Most cases result from nondisjunction during meiosis I

Question 27

Klinefelter Syndrome

Answer 27

* XXY * Males- testes small and man is sterile * Some breast enlargement and other female body characteristics are common * May have subnormal intelligence

Question 28

XYY

Answer 28

* Males- undergo normal sexual development * Tend to be somewhat taller than average

Question 29

Trisomy X (XXX)

Answer 29

* Females; Healthy * No unusual physical features other than being slightly taller than average * At risk for learning disabilities * Fertile

Question 30

Turner Syndrome

Answer 30

* Monosomy X (xo) * Only known viable monosomy in humans * Female; sterile because sex organs do not mature * When provided with estrogen replacement therapy, do develop secondary sex charateristics * Most have normal intelligence

Question 31

"Cri du chat"

Answer 31

* Cry of the Cat * Results from specific deletion in chromosome 5 * Severely intellectually disabled * Small head with unusal facial features * Cry that sounds like meowing of a distressed cat * Usually die in infancy or early childhood

Question 32

CML (Chronic Myelogenous Leukemia)

Answer 32

* Occurs when recriprocal translocation happens during mitosis of cells that will become WBC * Exchange of large portion of chromosome 22 with small fragment from a tip of chromosome 9 produces a much shortened chromosome 22 (Philadelphia Chromosome) * Causes cancer by activating a gene that leads to uncontrolled cell cycle progression

Question 33

A cross between homozygous purple flowered and homozygous white flowered pea plants results in offspring with purple flowers. This demonstartes...

Answer 33

Dominance

Question 34

Which of the following is (are) true for alleles? A) They can be dominant or recessive B) Thay can represent alternative forms of a gene C) They can be identical or different for any given gene in a somatic cell D) Only A and B E) A, B, And C

Answer 34

E

Question 35

P-purple, pp-white. The offspring of a cross between two heterozygous purple flowering plants (PpxPp) results in

Answer 35

Purple flowered plants and white flowered plants

Question 36

In snapdragons, heterozygotes have pink flowers, whereas homozygotes have red or white flowers. When plants with red flowers are crossed with plants with white flowers, what proportion of the offspring will have pink flowers?

Answer 36

100%

Question 37

Tallness (T) is dominant to dwarfness (t), while red (R) flower color is dominant to white (r). The heterozygous condition results in pink (Rr) flower color. A dwarf, red snapdragon is crossed with a plant homozygous for tallness and white flowers. What are the genotype and phenotype of the F1 individuals?

Answer 37

TtRr- tall and pink

Question 38

A woman who has blood type A, has a daughter who is type O positive and a son who is type B negative. Rh positive is a simple dominant trait over Rh negative. What is a possible genotype for the son?

Answer 38

BO

Question 39

A woman who has blood type A, has a daughter who is type O positive and a son who is type B negative. Rh positive is a simple dominant trait over Rh negative. What is a possible geneotype for the mother?

Answer 39

AO

Question 40

A woman who has blood type A, has a daughter who is type O positive and a son who is type B negative. Rh positive is a simple dominant trait over Rh negative. What is a possible genotype for the father?

Answer 40

B

Question 41

A woman and her spouse both show the normal phenotype for pigmentation, but both had one parent who was an albino. Albinism is an autosomal recessive trait. What is the probablity that their first child will be an albino?

Answer 41

1/4

Question 42

A woman and her spouse both show the normal phenotype for pigmentation, but both had one parent who was an albino. Albinism is an autosomal recessive trait. If their first two children have normal pigmementation, what is the probability that their thrid child will be albino?

Answer 42

1/4

Question 43

Huntington's Disease is caused by a dominant allele. If one of your parents has the disease, what is the probablility taht you, too, will have the disease?

Answer 43

1/2

Question 44

A woman has six sons. The chance that her next child will be a daughter is

Answer 44

1/2

Question 45

Substitution of the "wrong" amino acid in the hemoglobin protein results in this disorder.

Answer 45

Sickle-Cell Disease

Question 46

Individuals with this disorder are unable to metabolize certian lipids, affecting proper brain development. Affected individuals die in early childhood.

Answer 46

Tay-Sachs Disease

Question 47

This is caused by a dominant single gene defect and generally does not appear until the individual is 35-45 years of age.

Answer 47

Huntington's Disease