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BIO 303 > Exam 2 > Flashcards

Exam 2 Flashcards

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Biology 101 flashcards
1
Q

principle of segregation (Mendel’s first law)

A
  • Mendel’s first law

- separation of a gene pair during gamete formation

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2
Q

alleles

A
  • alternate forms of a gene

- “different flavors”

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3
Q

homozygous

A

-organisms with identical alleles for a gene

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4
Q

heterozygous

A

-organisms with different alleles for a gene

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5
Q

dihybrid cross

A
  • crossing parents with different traits
  • SSYY (smooth yellow) x ssyy (wrinkled green)
  • 9:3:3:1
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6
Q

principle of independent assortment

A
  • Mendel’s second law
  • explains inheritance of two traits
  • ex. 9:3:3:1 ratio in F2
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7
Q

locus

A

-specific site on chromosome that each gene is located on

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8
Q

incomplete dominance

A
  • expression of a phenotype that is intermediate to those of the parents
  • cross between 2 homologous dominant
  • ex. pink snapdragons (R1R2) made by dominant red (R1R1) and white (R2R2)
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9
Q

dominance

A
  • clearly defined dominant and recessive alleles and their corresponding phenotypes
  • RR (red) x rr (white) makes Rr (red)
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10
Q

codominance

A
  • full expression of both alleles is seen heterozygous
  • ex. blood type comes from codominant alleles of one I gene (IA, IB, and IO)
  • ex. red and white parents make red and white spotted flower (not pink)
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11
Q

exceptions to Mendel’s principles

A
  • ex. lethal yellow gene in mce
  • Yy yellow mice mate to make YY (dead), Yy (yellow), yy (nonyellow)
  • yellow gene is recessive for death, but dom for yellow coat color
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12
Q

sex chromosomes provide _____ path for embryo development that guides it towards a phenotypic sex

A

-genetic

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13
Q

phenotypic sex vs. chromosomal sex

A
  • phenotypes arise during embryonic development (may be different than chromosomal sex)
  • phenotypes can be opposite sex
  • can be intermediate of 2 sexes
  • can have characteristics and genitalia of both sexes
  • ex. fingerprints arise in womb
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14
Q

several levels that determine sex

A
  • chromosomal sex (XX vs. XY)
  • gonadal sex (ovaries vs. testes)
  • phenotypic sex (women built to give birth)
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15
Q

1st step in sex determination

A
  • chromosomal sex
  • occurs at fertilization
  • XX or XY
  • 50% chance of either
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16
Q

2nd step of sex determination

A
  • gonadal sex
  • if XY, SRY gene on Y chromosome signals gonad to develop into testes
  • if XX, lack of SRY gene
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17
Q

3rd step of sex determination

A
  • phenotypic sex
  • male: testosterone is converted to DHT which forms genitalia
  • female: lack of DHT prevents development of external genitalia
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18
Q

how many babies are born with phenotypic/ gonadal sex that is different than their chromosomal sex?

A

-1 in 2000 births

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19
Q

androgen insensitivity

A
  • mutation in the X-linked gene for the androgen receptor causes XY males to become phenotypic females
  • ex. Caster Semenya Olympic runner
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20
Q

pseudo hermaphroditism disorders

A
  • result in individuals with both male and female structures, but at different times in their lives
  • testosterone cat convert to DHT so XY don’t form testis/ appear female
  • born with vagina with large clit, develops into testicles ad penis during puberty
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21
Q

sex chromosomes

A
  • X and Y chromosomes
  • carry many genes that can be identified by unique inheritance pattern
  • X and Y have different patterns of inertance bc they carry different genes
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22
Q

who is affected by x-linked recessive disorders more?

A

-males (XY)

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23
Q

hemizygous

A
  • one chromosome pair rather than 2
  • all genes on the X chromosomes of males bc they only have one X
  • cant be heterozygous or homozygous for X-linked genes
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24
Q

sex chromosomes unique pattern of inheritance

A
  • males only give X to daughter and Y to son

- hetero females have 50% chances of passing X-linked recessive traits to male offspring

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25
Q

autosomal dominant

A
  • does not skip generations
  • affects both sexes equally
  • when one parent is affected the other one is not
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26
Q

x-linked dominant

A
  • dominant= every generation
  • males pass ONLY to daughters (not sons)
  • heterozygous affected females pass trait equally to sons and daughters
  • on average, twice as many daughters as sons affected
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27
Q

hypophosphatemia

A
  • x-linked dominant trait

- low phosphate in blood causes bowleggedness (like in dwarfs)

28
Q

autosomal recessive

A
  • skips at least 1 generation

- only if received two copies (one from each parent)

29
Q

x-linked recessive

A
  • recessive= skips at least one generation
  • phenotypic expression more common in males
  • affected males receive mutant allele from mom and pass to all daughters (not sons)
  • hemizygous males and homo females affected
  • daughters of male carriers are usually unaffected but sons have 50% chance
30
Q

color blindness (red and green) and white eye color in fruit flies

A
  • x-linked recessive trait

- affects 8% of males in US

31
Q

dosage compensation

A
  • mechanism that regulates the expression of sex-linked gene products
  • men and women produce same amount of X-gene products
  • allows certain x-linked recessive disorders to be expressed in heterozygous females
  • one inactive chromosome in females called barr body
32
Q

bar bodies

A
  • inactive, coiled up x chromosomes in cells
  • women can only express one X
  • wrinkled piece of paper that can be reopened later and passed on, just never used in that cell
33
Q

lyon hypothesis of how dosage compensation works

A
  • in heterozygous females, both alleles are active- but not in the same cell
  • permanent
  • random (either mom or dad’s X)
  • in somatic cells only (all cells other than repro)
  • inactivation of x chromosome happens early in development
34
Q

mosaicism

A
  • condition where cells in same organism express different genes
  • ex. tortoiseshell cat (only female)
    ex. blaschko’s lines
35
Q

in order for mosaicism to occur…

A
  • XX chromosomes
  • heterozygous on X cell
  • dosage compensation has to occur
36
Q

y-linked genes

A
  • traits are passed directly from father to son

- unique and uncommon

37
Q

incomplete penetrance

A

-when genotypes don’t always produce the expected phenotype

38
Q

penetrance

A
  • % of individuals having a particular genotype expressing the expected phenotype
  • if 38/42 people are polydactyly… 90% penetrance
  • relates to expressivity
39
Q

T/F: presence of a gene guarantees it will be expressed

A

false

40
Q

variation in phenotypic expression is caused by

A
  • age
  • genetic interactions
  • interactions with environment
41
Q

gene interaction

A
  • alleles of same gene exhibit independent assortment…. but do not act independently in their phenotypic expression
  • give perfect 9:3:3:1 or 3:1 ratio
42
Q

epistasis

A
  • gene interaction but with different genes (not the same one)
  • one gene masks affect of another gene at a different locus
  • ratio is off, 9:7
  • ex. balding gene doesn’t allow you to see what color hair offspring has
43
Q

sex-influenced traits

A
  • expressed in both sexes, but expressed differently in males and females
  • ex. pattern baldness is autosomal dom in males and recessive in females
  • related to x-linked male receptor gene (from mom)
44
Q

sex limited traits

A
  • inherited by both sexes, but normally expressed only in one sex phenotypically
  • ex. DMD/ muscular dystrophy only affects boys
45
Q

imprinting

A

-phenomenon where gene expression depends on if paternally or maternally inherited

46
Q

complex trait

A
  • determined by several gene pairs, nongenetic factors, and environmental interactions
  • ex. height in humans
47
Q

discontinuous characteristics

A
  • only 2 phenotypes

- tall or short pea plants

48
Q

continuous characteristics

A
  • distribution of phenotypic characters from one extreme to another in overlapping fashion
  • ex. human height
49
Q

polygenic traits

A
  • controlled by 2 or more gene pairs
  • typically have bell shaped curve
  • ex. eye color
50
Q

multifactorial traits

A
  • polygenic (controlled by 2 or more gene pairs) AND show interactions with environment (genes + nutrition = height)
  • ex. obesity
51
Q

larger number of loci controlling a trait means ___________.

A
  • more loci= more phenotypic classes
  • more phenotypes means less phenotypic difference between classes
  • ex. eye color (lots of colors, little difference between classes)
52
Q

principle of segregation

A
  • diploid (2n) organisms have two alleles at each locus on homologous chromosomes that separate in meiosis
  • one allele goes to each gamete
53
Q

independent assortment

A

-during the process of separation, both alleles at locus act independently of alleles at other loci

54
Q

recombination

A
  • sorting of alleles into new combinations

- result of independent separation of loci

55
Q

linked genes

A
  • genes located close together on the same chromosome
  • belong to same linkage group
  • usually inherited together/ don’t assort independently (skews mendelian ratios)
  • crossing over prevents this
56
Q

crossing over

A
  • occurs in prophase 1 of meiosis
  • prevents linked genes from assorting together
  • results in recombination (genetic reshuffling)
  • follows ratios
57
Q

writing linked genes

A

-must write linked genes on specific alleles like they are arranged on homologous chromosome
A B a b
———- X ————
A B a b

58
Q

cis configuration / coupling

A

-arrangement occurs when wild-type alleles are on one chromosome and mutant alleles on the other

59
Q

repulsion/ trans configuration

A

-occurs when wild-type allele and mutant allele of dif gene are found on same chromosome

60
Q

complete linkage

A
  • different genes are located very close to one another on same chromosome
  • all progeny are parental
  • ex. dwarf and mottled tomato plants
61
Q

how to test for linkage

A
  • testcross with heterozygous for both characteristics
  • if F2 resembles original traits they are nonrecombinant progeny (aka linked)
  • ex. (wont produce Md or mD in crosses)
62
Q

incomplete linkage

A
  • genes that exhibit crossing over
  • most progeny are parental
  • produce recombinant progeny (different allele combos than parents)
63
Q

recombination frequency

A
  • % recombinant progeny produced in a cross (50% max)
  • # recombinant progeny / total # progeny X100
  • lead to genetic maps by Hunt
64
Q

physical maps

A

-using exact base pairs btwn loci, more refined, came with new technology

65
Q

genetic maps

A
  • based off of one another, recombination theories
  • uses approximations
  • measured in m.u. or cM
  • underestimate

BIO 303 (4 decks)

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