Genetics

Question 1

Law of segregation

Answer 1

follows 1 single character
- monohybrids
- monohybrids cross

Question 2

monohybrids

Answer 2

heterozygous for one character (Pp); F1 offspring

Question 3

monohybrid cross

Answer 3

Pp x Pp

Question 4

the law of independent assortment

Answer 4

followed two characters; each pair of alleles segregates independently of any other pair during games formation
- dihybrids
- hypothesis of dependent assortment wrong
- law applies to genes on chromosomes that are not homologs or those far apart on same chromosome
- genes located near each other are inherited together

Question 5

dihybrids

Answer 5

heterozygous for both characters (YyRr); crossing two true-breeding parents differing in two characters produces this

Question 6

dihybrid cross

Answer 6

cross between F1 hybrids; determines whether two characters are transmitted to offspring as a package or independently

Question 7

Mendel’s law of segregation and independent assortment reflect…

Answer 7

the rules of probability

Question 8

the multiplication rule

Answer 8

the probability that two or more independent events will occur together is the product of their individual probabilities

Question 9

the addition rule

Answer 9

the probability that any one or two or more mutually exclusive events will occur is calculated by adding together their individual probabilities

Question 10

inheritance of character by single gene may deviate from simple Mendelian patterns in the following situations

Answer 10

• when alleles are not completely dominant or recessive
• when a gene has more than two alleles
• when a single gene produces multiple phenotype

Question 11

complete dominance

Answer 11

occurs when phenotypes of the heterozygous and dominant homozygous are identical (PP or Pp)

Question 12

incomplete dominance

Answer 12

the phenotype of F1 hybrids is somewhere between the phenotypes of the two parental varieties

Question 13

codominace

Answer 13

two equally dominant alleles, both phenotypes will show up in the heterozygote

Question 14

dominant alleles are not necessarily more common in populations than..

Answer 14

recessive alleles

Question 15

most ones exist in population in more than…

Answer 15

two allelic forms
- ex: IA, IB, i

Question 16

pleiotropy

Answer 16

genes have multiple phenotypic effects
- ex: one gene causes multiple diseases

Question 17

epistasis

Answer 17

a gene at one locus alters the phenotypic expression of a gene at a second locus

Question 18

quantitative characters

Answer 18

are those that vary in the population along a continuum - usually indicate polygenic inheritance

Question 19

polygenic inheritance

Answer 19

are additive effect of two or more genes on a single phenotype
- broad phenotypic range

Question 20

multifactorial

Answer 20

genetic and environmental factors collectively influence phenotype

Question 21

Why are humans not good genetic research subjects?

Answer 21

• generation time is too long
• humans produce relatively few offspring
• breeding experiments are unacceptable

Question 22

pedigree

Answer 22

a family tree that describes the interrelationships of parents and children across generations
- inheritance patterns of particular traits can be traced
- can be used to make predictions about future offspring

Question 23

Many genetic disorders are inherited in a recessive manner

Answer 23

Albinism, sickle cell disease

Question 24

Carriers

Answer 24

heterozygous individuals who carry the recessive alleles but are phenotypically normal
- recessive disorder babies (aa) born to them
- consanguineous (close relative sex) ups chances of diseased baby

Question 25

cystic fibrosis

Answer 25

most common lethal genetic disease in the US
- allele results in defective/absent chloride transport channels

Question 26

Sickle Cell disease

Answer 26

homozygous, all hemoglobin is abnormal
- African, substitute of 1 AA in hemoglobin protein
- heterozygous: usually healthy but have symptoms
- less susceptible to malaria

Question 27

some human disorders are caused by dominant alleles

Answer 27

• rare and arise from dominant alleles
• dwarfism type is an example

Question 28

the timing of onset of a disease affects…

Answer 28

its inheritance
- Huntington’s disease is lethal but doesn’t show up until 45

Question 29

____ has a tremendous effect on phenotype for cardiovascular health and other multifactorial characters

Answer 29

lifestyle

Question 30

Sex-linked genes exhibit unique patterns of inheritance

Answer 30

• small X chromosome and large Y chromosome (women:XX male:XY)
• only ends of Y chromosome have regions that are homologous with corresponding regions of the X chromosome
• the SRY gene on Y is required for testes
• only for mammals

Question 31

sex-linked gene

Answer 31

A gene that is located on either sex chromosome
- genes on Y are called Y linked genes
- genes on X are called X-linked genes

Question 32

Most Y-linked genes help determine Sex but X chromosomes….

Answer 32

have genes for many characters unrelated to sex - X-linked genes follow specific patterns of inheritance

Question 33

For a recessive X-linked trait to be expressed:

Answer 33

• a female needs two copies of the alleles (homozygous)
• a male needs only one copy of the allele (heterozygous)
• much more common in males