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DAT > Biology-Heredity > Flashcards

Biology-Heredity Flashcards

1
Q

multiplication rule

A

you use this to determine the probability of two or more independent events occurring together, you multiply the probabilities of each event happening separately

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2
Q

gene

A

genetic material on a chromosome that contains the instructions for creating a particular trait

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3
Q

allele

A

one of several varieties of a gene

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4
Q

locus

A

location on a chromosome where a gene is located. Every gene has a unique locus on a particular chromosome

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5
Q

homologous chromosomes

A

refer to a pair of chromosomes (a homologous pair) that contains the same genetic info, gene for gene.

Each parent contributed 1 of the chromosome in the pair and thus different alleles may exist for a gene (dominant and recessive or incomplete dominance (color blending)/ co-dominant such as blood type).

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6
Q

dominant

A

actual trait that is expressed

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7
Q

homozygous dominant

A

refers to the inheritance of two dominant alleles (PP)

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8
Q

heterozygous

A

refers to the condition where two inherited alleles are different (Pp)

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9
Q

phenotype

A

actual expression of a gene

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10
Q

genotype

A

represents actual alleles

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11
Q

Mendel

A

credited w/ the discovery of the laws of segregation and independent assortment

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12
Q

law of segregation

A

refers to the segregation (separation) of alleles (and their chromosomes) to individual gametes

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 chromosome), occurs in anaphase I.

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13
Q

law of independent assortment

A

refers to the independent assortment of alleles (and chromosomes)

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

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14
Q

Monohybrid cross

A

An experiment in which only one trait is being investigated

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15
Q

Dihybrid cross

A

An experiment where two traits are being investigated

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16
Q

Complete (full) dominance

A

When traits are expressed as if one allele is dominant to a second allele

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17
Q

Test Cross

A

Mating of an individual whose genotype you are trying to determine with an individual whose genotype is known

unknown dominant genotype x homozygous recessive phenotype to determine if hetero or homo dominant

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18
Q

Incomplete dominance

A

Blending of the individual expressions of the two alleles

e.g. R red, R’ white, RR’ comes out pink

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19
Q

Codominance

A

Both inherited alleles are completely expressed

e.g. blood types A and B or both can show up as AB if expressed

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20
Q

Antigens

A

Foreign substances (immune system)

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21
Q

Antibodies

A

Attack the antigens

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22
Q

Agglutination

A

Clumping of the blood that may result in death

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23
Q

Epistasis

A

Occurs when one gene affects the phenotypic express of a second gene

Pigmentation (one gene controls (turn on/off) the production of pigment, and 2nd gene controls color or amount). IF 1st gene codes for no pigment —> 2nd gene has no effect

CCBx => black fur in mice

ccxx => no pigment

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24
Q

Pleiotropy

A

Occurs when a single gene has more than one phenotypic expression (gene in pea plants that expressed seed texture also influences phenotype of starch metabolism and water uptake; sickle cell anemia leads to different health conditions).

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25
Q

Sickle cell disease

A

A human blood disorder that is caused by an allele that incorrectly codes for hemoglobin

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26
Q

Polygenic inheritance

A

The interaction of many genes to shape a single phenotype, which is the opposite of pleiotropy (one gene influences many phenotypes)

(height, skin color)

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27
Q

linked genes

A

genes that reside on the same chromosome and thus cannot segregate independently because they are physically connected. Linked genes exhibit recombination about 18% of the time.

In a cross of BbVv X bbvv (says that BV and bv are linked and each is in a homologues). We only get BV or bv and no Bv or bV. However, if there is recombination, we may get 18% of Bv and bV.

28
Q

In which phase do linked genes cross over?

A

prophase I

29
Q

linkage map

A

portrayal of the gene sequence on a chromosome

30
Q

cytological map

A

a map that portrays the true relative positions of the genes, which requires additional experimental analysis

31
Q

sex chromosomes

A

the X and Y chromosomes

32
Q

autosomes

A

all chromosomes excluding the sex ones

33
Q

sex-linked (or X-linked) genes

A

genes that reside on the X, or sex, chromosome; Y-linked are also possible.

when male (XY) receives an X from mother, whether it is dominant or recessive will be expressed because there is no copy on the Y chromosome.

34
Q

X-inactivation

A

one of the two X chromosomes in each cell does not uncoil into a chromatin => dark and coiled compact body chromosome (Barr body) => cannot be expressed. All cells in a female mammal are not necessarily functionally identical

Hemophilia: cannot form blood clot. X^H X^h is a normal carrier. But if X^H is inactivated => X^h is expressed

35
Q

Barr body

A

one chromosome remains coiled as a dark, compact body

36
Q

Nondisjunction

A

failure of one or more chromosome pairs or chromatids of a single chromosome to properly separate during mitosis (failure of two chromatids of a single chromosome during anaphase) or meiosis ( homologous chromosomes to separate during Meiosis I or sister chromatids to separate during Meiosis II; result in trisomy or monosomy; ex. Down Syndrome

specifically during anaphase!

37
Q

mosaicism

A

a fraction of the body cells, those descendent of a cell where nondisjunction occurs, have an extra or missing chromosome

38
Q

Polyploidy

A

occurs if all of the chromosomes undergo meiotic nondisjunction and produce gametes w/ twice the number of chromosomes. Common in plants

39
Q

Point Mutations

A

occur when a single nucleotide in the DNA of a gene is incorrect causing substitution, insertion, or deletion (latter 2 could cause frameshift); most have deleterious effects on gene function

40
Q

(point mutation) Substitution

A

occurs when a different nucleotide is substituted for the correct one

41
Q

(point mutation) Deletion

A

occurs when a nucleotide base-pair is omitted

42
Q

(point mutation) Insertion

A

occurs if an extra base pair is inserted

43
Q

Aneuploidy

A

a genome w/ extra or missing chromosomes XO sterile, physically abnormal; Klinefelter (XXY); Down Syndrome (Trisomy 21)

44
Q

Down syndrome

A

occurs when an egg or sperm w/ an extra number 21 chromosome fuses w/ a normal gamete. The result is a zygote with 3 copies of chromosome 21 (trisomy).

45
Q

Turner Syndrome

A

results when there is nondisjunction of the sex chromosomes. Sperm will have either both sex chromosomes (XY) or no sex chromosomes (O). Similarly, eggs will be either XX or O.

A Turner syndrome zygote (XO) is a female who has one X and no second chromosome

46
Q

chromosomal aberrations

A

caused when chromosome segments are changed:

  • Duplications
  • Inversions
  • Translocations
47
Q

(chromosomal aberrations) Duplications

A

chromosome segment is repeated on the same chromosome

48
Q

(chromosomal aberrations) Inversions

A

chromosome segments are rearranged in reverse orientation on the same chromosome

49
Q

(chromosomal aberrations) Translocations

A

segment of a chromosome is moved to another chromosome

(21 on 14 can cause Down’s as well, tripled 21 chunk: 3 copies of a segment from chromosome 21 ( two chromosomes 21 and a chromosome 14 with a segment of chromosome 21)

50
Q

multiple alleles

A

blood groups have 3 possible alleles, the codominant A and B and the O, leading to 4 possible phenotypes: AO (A type) BO (B type) AB (codominant AB type), OO (O type)

51
Q

transition mutation

A

purine to purine or pyrimidine to pyrimidine

52
Q

transversion mutation

A

purine to pyrimidine or vice versa

53
Q

chromosomal breakage (human genetic defects)

A

spontaneous or induced (mutagenic agents, Xrays). Deficiency = lost fragment

54
Q

mutagenic agents

A

cosmic rays, Xrays, UV rays, radioactivity, chemical compounds include colchicine (inhibits spindle formation causing polyploidy), mustard gas. Mutagenic agents are generally also carcinogenic

-Proto-oncogenes stimulate normal growth; if mutated become oncogenes => cancer

55
Q

Genetic disorders include:

A

AR: PKU (inability to produce proper enzyme for phenylalanine breakdown; degradation product phenylpyruvic acid accumulates)

cystic fibrosis (fluid buildup in tracts)

Tay-sachs (lysosome defect, can’t breakdown lipids for normal brain fxn)

sickle-cell (defective hemoglobin due to substitution mutation)

AD: Huntingtons (degenerate nervous system disease

SLR: hemophilia (abnormal blood clotting, color blind, duchenne (muscular dystrophy)

Chromosomal: Downs, Turner (XO), Klinefelter (XXY), Sickle-cell anemia

56
Q

forward mutation

A

already mutated organism mutates again even more

57
Q

backward mutation

A

mutates back to original

58
Q

extranuclear inheritance

A

extranuclear genes are found in mitochondria and chloroplasts. Defects in mito DNA can reduce cell’s ATP production. Mitochondria passed to zygote all come from mother, so all related diseases are mother inherited.

NOTE: mitochrondria have their own 70S ribosomes that make mitochondrial proteins w/in mitochondrial matrix

59
Q

lethal gene

A

cross between Aa and Aa, we get AA:2Aa:aa. If “aa” was lethal, we would have AA and Aa as 1:2 ratio

60
Q

hemizygous

A

one single copy instead of two

61
Q

Tips

A

IF the phenotype “skips” generations be suspicious of an autosomal recessive disorder

IF no skip, most likely an autosomal dominant disorder

Be suspicious for x-linked recessive, if a father doesn’t have the phenotype, none of his daughters display it

62
Q

Partial Monosomy

A

When only part of one chromosome is lost

63
Q

Partial trisomy

A

Addition of only a portion of another chromosome is seen

64
Q

Partial Monosomy

A

When only part of one chromosome is lost

65
Q

Partial trisomy

A

Addition of only a portion of another chromosome is seen

DAT (18 decks)

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