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DAT Biology > 6. Heredity + > Flashcards

6. Heredity + Flashcards

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1
Q

Gene

A
  • genetic material on a chromosome for a trait
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2
Q

Locus

A
  • location on chromosome where gene is located
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3
Q

Allele

A
  • variance of genes such as different color
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4
Q

Homologous Chromosomes

A
  • a pair of chromosomes that contain same genetic material (gene for gene).
  • each parent contributed 1 of the chromosome pair and thus different alleles might exist
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5
Q

Law of Segregation

A
  • one member of each chromosome pair migrates to opposite pole so that each gamete is haploid
  • occurs in anaphase I
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6
Q

Law of Independent Assortment

A
  • migration of homologues within one pair of chromosomes doesn’t influence migration of other homologous pairs.
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7
Q

Test Crosses

A
  • monohybrid: test one gene
  • dihybrid: test two genes (on different chromosomes)
  • unknown dominant genotype x homozygous recc to determine if hetero or homo dominant
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8
Q

Incomplete Dominance

A
  • blending of expressions of alleles
  • unique hetero phenotype
  • R = red, r = white, Rr= pink
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9
Q

Codominance

A
  • both inherited alleles are expressed

- ex. blood type. blood type AB is codominance of A and B

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10
Q

Multiple Alleles

A
  • blood groups have three alleles, A, B, O, 6 genotypes
  • AO or AA -> A type
  • BO or BB -> B type
  • AB -> codominant AB type
  • OO -> O type
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11
Q

Epistasis

A
  • one gene affects phenotypic expression of second gene
  • ex. pigmentation. one gene turns on production of pigment, another gene controls color or amount. if first gene is turned off, then no pigment is produced. ex. fur color in mice
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12
Q

Pleitropy

A
  • single gene has more than 1 phenotypic expression
  • ex. gene in pea plants that codes for seed texture also influences starch metabolism and water uptake
  • ex. sickle cell anemia leads to diff health conditions
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13
Q

Polygenic Inheritance

A
  • interaction of many genes to shape a single phenotype w/ continuous variation (height, skin color)
  • opposite of pleitropy
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14
Q

Linked Genes

A
  • two or more genes that reside on same chromosome and cannot separate independently because they are physically connected (inherited together)
  • linked genes exhibit recombination about 18 % of time
  • greater recomb. freq. (above 18%) means farther distance of genes on same chromosome
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15
Q

Linkage Map

A

B-V is 18% A-V is 12%, and B-A is 6%

B—–A————-V

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16
Q

Sex-Linked

A
  • single gene resides on sex chromosome
  • when male (XY) receives an X from mother, whether it is dominant or recessive, it will be expressed bec there is no copy on Y chromosome
17
Q

Sex-influenced

A
  • can be influenced by sex of individual carrying trait

- ex. Bb female not bald, Bb male is bald

18
Q

Sex Chromosomes v. Autosomes

A
  • sex chromosomes: pair of homologous chromosomes that doesn’t have exactly the same genes, X, Y
  • autosomes: all other chromosomes
19
Q

Hemophilia

A
  • sex-linked recessive
  • hemophiliacs cannot properly form blood clots and in worst cases can die from minor injuries by bleeding to death
  • in order for female to be a hemophiliac, she must have two copies of the defective allele, a male needs only one defective copy -> as a result, hemophilia and other sex-linked genetic defects are much more common in males.
  • heterozygous females have normal clotting abilities but are said to be carriers
20
Q

Penetrance

A
  • probability an organism w/ a specific genotype will express a particular phenotype
21
Q

Expressivity

A
  • term describing variation of phenotype for a specific genotype
22
Q

X-inactivation

A
  • during embryonic development in female mammals, one of two x chromosomes does not uncoil into chromatin -> dark and coiled compact body chromosome (barr body) -> can’t be expressed
  • either chromosome can be inactivated -> genes in female will not be expressed similarly, so all cells in a female mammal are not necessarily functionally identical (some have one x inactivated, others have the other x inactivated) (calico cats)
  • what does this mean for sex-linked defects such as hemophilia? carrier female (Hh) is usually normal but it is possible that all cells producing the clotting factor H are inactivated -> smae symptoms of hemophilia as a male
23
Q

Nondisjunction

A
  • failure of chromosme separation
  • failure of sister chromatids to separate during anaphase of mitosis
  • failure of homologous chromosmes to separate during anaphase I of meiosis
  • failure of sister chromatids to separate during anaphase II of meiosis
24
Q

Mosaicism

A
  • nondisjunction in mitosis during embryonic development

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

25
Q

Polyploidy

A
  • all chromosomes undergo meiotic nondisjunction and produce gametes w/ twice the number of chromosomes.
  • common in plants
26
Q

Point Mutation

A
  • single nucleotide changes causing substitution, insertion, or deletion (latter 2 could cause frameshift)
  • transition mutation: purine to purine or pyrim to pyrim
  • transversion mutation: purine to pyrim or pyrim to purine
27
Q

Aneuploidy

A
  • genome w/ extra/missing chromosome
  • often caused by nondisjunction
  • down syndrome (trisomy 21)
  • turner syndrome: nondisjunction in sex-chromosome. resulting in abnormal gametes: XX, XY, O. zygote XO -> sterile, physically abnormal
  • Klinefelter: XXY
28
Q

Chromosomal Aberrations

A
  • duplications: chromsome segment repeated on same chromosome
  • inversion: chromosome segment rearranged in reverse on same chromosome
  • translocation: segment of chromosome moved to another chromosme. sometimes can result in down syndrome. ex. translocation of segment from 21 to 14 - > individual would inherit three copies of a segment of chromsome 21 (two chromsomes 21 and 14/21 chromosome) -> same phenotypic effect as trisomy 21
29
Q

Mutagenic Agents

A
  • include cosmic rays, xrays, uv rays, radioactiity, chemical compounds (cholchicine -> inhibit spindle formation), mustard gas.
  • mutagenic agents are generally also carcinogenic
  • proto-oncogenes stimulate normal growth, if mutated become oncogenes -> cancer
30
Q

Genetic Disorders

A
  • Autosomal recessive:
    a. PKU - inability to produce proper enzyme for phenylalanine breakdown
    b. cystic fibrosis - fluid buildup in tracts
    c. Tay-sachs -lysosome defect, can’t breakdown lipids for normal brain function
    d. sickle cell - defective hemoglobin do to subst mutation
  • Autosomal dominant
    a. Huntington’s - degenerate nervous system disease
  • Sex-linkd recessive
    a. hemophilia - abnormal blood clotting
    b. color blindness
    c. duchenne - muscular dystrophy
  • Chromosomal
    a. down syndrome
    b. turner - XO
    c. klinefelter - XXY
    d. Cri Du Chat - deletion on chromosome 5
  • turner’s doesn’t usually cause mental retardation, but downs, kline, and cri du chat do.
31
Q

Forward vs. Backward Mutations

A
  • forward: already mutated organism mutates again

- backward: already mutated goes back to original

32
Q

Extranuclear Inheritance

A
  • extranuclear genes found in mitochondria and chloroplasts.
  • defects in mitochondria’s DNA can reduce ATP production
  • mitochondria all come from mother, so all related diseases are inherited from mother.
  • mitochondria have their own ~ 70S ribosomes that make mitochondrial proteins w/in mitochondrial matrix
33
Q

Homozygous

A
  • two copies of same allele

- AA or aa

34
Q

Heterozygous

A
  • different alleles of same gene

- Aa

35
Q

Hemizygous

A
  • one single copy of a gene instead of two

- male has XY sex chromosome -> hemizygous

36
Q

Genetic Family Pedigree

A
  • if phenotype “skips” generations -> be suspicious of an autosomal recessive disorder
  • if no “skip” then most likely autosomal dominant.
  • be suspicious for x-linked recessive - > if a father doesn’t have the phenotype then none of his daughters display it

DAT Biology (19 decks)

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