Chapter 6: Heredity

Question 1

multiplication rule

Answer 1

to determine the probability of two or more independent events occurring together multiply the probabilities of each separate event

Question 2

gene

Answer 2

genetic material on a chromosome for a trait

Question 3

allele

Answer 3

variance of genes such as different color

Question 4

locus

Answer 4

location on chromosome where gene is located

Question 5

homologous chromosome

Answer 5

1. a pair of chromosomes that contains same genetic material (gene for gene)
2. each parent contributed 1 of the chromosomes in the pair and this different alleles may exist for a gene (dominant and recessive or incomplete dominance (color blending)/ co-dominant such as blood type)

Question 6

law of segregation

Answer 6

one member of each chromosome pair migrates to an opposite pole so that each gamete is haploid (aka each gamete has only one copy of each allele)
— occurs in anaphase 1

Question 7

law of independent assortment

Answer 7

migration of homologues within one pair of homologous chromosomes does not influence the migration of homologues of other homologous pairs (independent assortment of alleles)

Question 8

test crosses

Answer 8

1. monohybrid crosses test one gene
2. dihybrid test two (on different chromosomes)
3. crosses have P, F1, F2, etc generations
4. You can cross (unknown dominant genotype) X (homozygous recessive) to determine if hetero or homo dominant
5. to determine probabilities in dihyrbrid, usually easier to calculate probability of each gene separately then multiply

Question 9

incomplete dominance

Answer 9

blending of expressions of alleles (R= red, R’=white, RR’=pink

Question 10

codominance

Answer 10

1. both inherited alleles are completely expressed

2. Blood types A and B or both can show up as AB if expressed

Question 11

multiple alleles

Answer 11

1. Blood groups have 3 possible alleles
2. the codominant A and B and the O, leading to 4 possible phenotypes (6 possible genotypes)
3. AO/AA (A type)
4. BO/BB (B type)
5. AB (AB type)
6. OO (O type)

Question 12

epistasis

Answer 12

1. one gene affects phenotypic expression of 2nd gene.
2. Pigmentation (one gene controls (turn on/off) the production of pigment, and 2nd gene controls color or amount
3. If 1st gene codes for no pigment => 2nd gene has no effect
   CCBx=> black fur ccxx=no pigment

Question 13

pleiotropy

Answer 13

1. single gene has more than 1 phenotypic expression
2. gene in pea plants that expessed seed texture also influences phenotype of starch metabolism and water uptake; sickle cell anemia leads to different health conditions

Question 14

polygenic inheritance

Answer 14

the interaction of many genes to shape a single phenotype w/ continuous variation (height, skin color in humans)

Question 15

linked genes

Answer 15

1. two or more genes that reside on the same chromosomes and this cannot separate independently because they are physically connected (inherited together)
2. linked genes exhibit recombination about 18% of the time?
3. In a cross of BbVv x bbvv (says that BV and bv are linked and is in a homologue)
4. we can only get BV and bv and no Bv or bV
5. however, if there is recombination, we may get 18% Bv and bV
6. the greater the recombination frequencies (18% above) means farther distance apart on the same chromosome.

Question 16

linkage map

Answer 16

B-V is 18%, A-V is 12%, B-A is 6%=>

B——A————V

Question 17

sex-linked

Answer 17

1. refers to single gene resides on X chromosome
2. when male (XY) receives an X from mother, whether it is dominant of recessive will be expressed because there is no copy on the Y chromosome

Question 18

sex-influenced

Answer 18

can be influenced by sex of individual carrying trait (Bb female not bald, Bb male is)

Question 19

penetrance

Answer 19

probability an organism with a specific genotype will express a particular phenotype

Question 20

expressivity

Answer 20

term describing the variation of phenotype for a specific genotype

Question 21

X-inactivation

Answer 21

1. during embryonic development in female mammals, one o two X chromosomes does not uncoil into chromatin=> dark and coiled compact body chromosome (Barr body)=> cannot be expressed
2. Thus, only the genes on the other X chromosomes will be expressed.
3. either one can be inactivated=> genes in the female will not be expressed similarly, so all cells in a female mammal not necessarily functionally identical (calico cats)

Question 22

hemophilia

Answer 22

cannot form blood clot. XHXh is normal carrier. But if XH is inactivated=> Xh is expressed

Question 23

nondisjunction

Answer 23

1. failure of one/more chromosomes pairs or chromatids to separate during mitosis
2. failure of two chromatids of a single chromosome during anaphase or meiosis ( homologous chromosomes to separate during meiosis 1 or sister chromatids to separate during meisosi 2; result in trisomy or monosomy; ex down syndrome ** note specifically during anaphase

Question 24

mosaicism

Answer 24

in cells that undergo nondisjunction in mitosis during embryonic development; fraction of body cells have extra or missing chromosome

Question 25

polyploidy

Answer 25

all chromosomes undergo meiotic nondisjunction and produce gametes with twice the number of chromosomes. Common in plants.

Question 26

point mutation

Answer 26

1. single nucleotide changes causing substitution, insertion, deletion (latter 2 could use frameshift)
2. transition mutation: purine to purine or pyrimidine to pyrimidine
3. transverse mutation: purine to pyridine or vice versa

Question 27

aneuploidy

Answer 27

genome with extra/missing chromosome<= often caused by nondisjunction (down syndrome =trisomy 21)

Question 28

turner syndrome

Answer 28

1. nondisjunction in sex chromosome
2. gametes (single, frome one parent) can be XX/XY or O (no chromosome)=> XO sterile, physically abnormal
3. klinefelter (XXY); down syndrome (trisomy 21)

Question 29

chromosomal abberations

Answer 29

chromosome segments are changed

Question 30

duplications

Answer 30

chromosome segment is repeated on same chromo

Question 31

inversions

Answer 31

chromosome segments are rearranged in reverse orientation

Question 32

translocation

Answer 32

segment is moved to another chromosome. Can be reciprocal (two non-homolgous chromosomes swap chuncks or Robertsonian (one chromo from a pair becomes attached to another from a pair
e.g. an extra chromo 21 attached to 14 can cause down syndrome as well