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Animal Biology > Genetics > Flashcards

Genetics Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Chromosomes

A

complex of DNA w/ histone protein
Visible in a dividing cell.
# of chromosomes is constant for a species
Humans 46 (22 pairs of autosomes and 1 pr of sex) in each somatic cell
Not all chromatin is equally active; some genes are active in only certain cells or certain phases of life

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2
Q

Sex & autosome chromosomes

A

Sex determine sex & sex-linked traits; X & Y chromosomes do not carry same genes
Autosomes determine all other characteristics

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3
Q

Homologous chromosomes

A

pairs of chromosomes, one from each parent; contain similar but not the same genes (alleles) coding for same set of characteristics

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4
Q

Haploid (n)

A

Single set of chromosomes (one member of each homologous pair)

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5
Q

gamete

A

possesses only one haploid (n)

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6
Q

Zygote

A

when two gametes unite in fertilization, it results in two sets of chromosomes or diploid (2n)

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7
Q

Human zygote & all somatic cells

A

2n = 46

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8
Q

Gamete

A

n = 23

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9
Q

Mitosis

A
  1. responsible for growth, replacement of damaged somatic cells
  2. responsible for producing a multicellular organism from a single-celled zygote
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10
Q

Mitosis in asexually reproducing animals

A

Transfers genetic information from parent to progeny

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11
Q

Daughter cells in mitosis

A

Each one is ID to parent cell but can later differentiate by differential gene expression

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12
Q

Cell division by mitosis

A

consists of a division of nuclear chromosomes (mitosis) followed by the division of cytoplasm (cytokinesis)

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13
Q

Cell cycle

A 
Interphase
Prophase
Metaphase
Anaphase
Telophase
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14
Q

Prophase

A
  1. Nuclear envelope disintegrates
  2. Centrosomes replicate; two centrioles migrate to opposite poles of cell
  3. Microtubules join centrioles to form spindle
  4. Chromatin condenses into chromosomes: each has 2 id sister chomatids (formed by DNA replication) joined at their centromere
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15
Q

Metaphase

A

Chromosomes line up in the middle of the nucleus

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16
Q

Anaphase

A

Sister Chromatids seperate at the centromere and move to opposite poles of nucleus, pulled by centrioles. Each pole now has complete set of chromosomes

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17
Q

Telophase

A

Spindle disappears and chromosomes diffuse into chromatin. Nuclear envelope reappears.

18
Q

Cell division via Meiosis

A
  1. Unlike mitosis, daughter cells are not genetically id to each other or to parent cell.
  2. Sexual reproduction requires genetic contribution from two sex cells (gametes), which unite & form zygote
  3. To maintain # of chromosomes constant in next generation, the gametes must have 1/2 # of chromosomes as somatic cells
19
Q

gene

A

a unit of heredity that is transferred from a parent to offspring and is held to determine some characteristic of the offspring.

20
Q

Meiosis I

A
  1. Similar to mitosis, each chromosome replicates & has 2 chromatids, joined at the centromere.
  2. Four chromatids of homologous pair come into synapsis (side by side contact), permitting crossing over (genetic recombination) between nonsister chromatids
  3. Unlike mitosis, centromere does not divide. One entire chromosome (that has 2 chromatids) from each homologous pair, is pulled into each daughter cell.
  4. At end of Meiosis I, each of 2 daughter cells contains one chromosome of each homologous pair (therefore haploid) but as each chromosome still contains the two chromatids, each cell has twice the amount of DNA.
21
Q

Homologous chromosomes break and . . .

A

exchange genes; increasing the amt of genetic variation.

Recombination frequency of two loci is directly proportional to the distance between them.

22
Q

Meiosis II

A
  1. The second meiotic division resembles mitosis.
  2. Sister chromatids separate at anaphase
  3. Each daughter cell now haploid & has normal amt of DNA
  4. Four haploid cells formed from 1 diploid cell as result of meiosis. Each cell has only one copy of each chromosome (one copy of each gene).
23
Q

Mendel’s 2 Laws of Inheritance: #1:LAW OF SEGREGATION

A
  1. Law of Segregation: gametes form, paired chromosomes (& genes) specifying alternative phenotypes separate; each gamete receives onluy one of two alternative copies of genes (alleles).
    When paired alleles are alike in the two homologous chromosomes, the individual is a homozygote; if unlike, heterozygote
    Allele expressed in heterozygote is dominant and the allele that is not is recessive
    SHOWS THAT THERE IS NO BLENDING OF TRAITS BECAUSE NONE OF PROGENY HAS AN INTERMEDIATE CHARACTER BUT RATHER HAS ONLY ONE OF THE TWO POSSIBLE CHARACTERS.
24
Q

2: LAW OF INDEPENDENT ASSORTMENT

A

Genes located on different pairs of homologous chromosomes assort independently during meiosis.

25
Q

Mono- & di-hybrid cross/ratios to demonstrate Mendel’s laws

A

MUST LOOK AT SLIDES

26
Q

Molecular basis of inheritance

A

The dominant allele codes for a functional protein; the recessive allele codes for a non-functional one.

27
Q

Deviations from Mendel’s Laws

A
  1. Not all traits are inherited by simple Mendelian laws.
  2. Mendel avoided traits that were inherited under different rules.
  3. Numerous factors can cause traits to be inherited in ways that differ from simple Mendelian genetics.
28
Q

Deviation #1: Incomplete dominance or codominance

A

Both alleles are expressed equally (produce functional proteins) & the heterogynous phenotype is intermediate-a blending of the two parental types. ie ABO blood types

29
Q

Deviation #2: Polygenic or quantitative inheritance

A

Multiple genes affect a single characteristic. Polygenic characteristics show continuous variation NOT discrete alternatives ie height, skin color

30
Q

Deviation #3: Sex-linked inheritance

A

Recessive traits are carried on the X chromosome.
For the trait to be expressed:
a) in a female, both alleles have to recessive
b) in a male, only one recessive is sufficient since the male has only one X chromosome
A herterogynous female with one recessive allele is a CARRIER for the allele but is phenotypically normal. Therefore the males outnumber females in expression of the trait.

31
Q

Deviation #4: Linkage

A

All traits do not assort independently, contrary to Mendel’s 2nd Law. All genes and therefore traits present on a single chromosome are LINKED & are inherited together. So there are as many linkage groups as there are chromosome pairs.
Linked traits can seperate due to seperation of alleles located on the same chromosome - crossing over or recombination.

32
Q

Sources of Phenotypic Variation

A
  1. Reshuffling of existing genetic diversity due to sexual reproduction and meiosis via:
    a) independent assortment of chromosomes during meiosis
    b) Crossing over during meiosis
    c) fusion of random gametes from both parents
  2. New genetic variations via mutations
33
Q

Definition of Mutations

A

random changes in nucleotide sequence that could produce either beneficial or harmful effects. Occur spontaneously due to base pairing errors during replication.

34
Q

Facts about mutations:

A
  1. Mutation in somatic cells are not important for evolution
  2. Most mutations recessive and therefore masked by partner’s alleles. A population carries a pool of recessive alleles without being expressed
  3. Mutation rates vary at different loci. A long gene is more like to mutate than a short gene.
  4. About every 3rd persons carries one new mutation.
35
Q

Chromosomal Aberrations

A
  1. Numerical

2. Structural

36
Q
  1. Numerical Aberrations
A

Euploidy: addition or deletion of one (aneuploidy) or more (polyploidy) chromosomes.

37
Q

Aneuploidy

A

caused by failure of chromosomes to seperate during meiosis (nondisjunction). As a result, both chromosomes go to one pole and none to other, producing one gamete having n-1 chromosome and other with n+1 chromosomes

38
Q

Monosomy

A

Result of a n-1 gamete fusing with a normal n gamete. Survival is rare due to lack of genetic instructions.

39
Q

Trisomy

A

Result of an n+1 gamete fusing with a normal n gamete. ie Downs syndrome (appears > with increasing age of mother but not father)

40
Q

FAct re: seperation during meiosis or disjunction

A

Since a cell only requires 1 functional X chromosome, non-disjunction of X chromosome is better tolerated but still leads to abnormalities

41
Q

XXY

A

Klinefelter Syndrome: phenotypically male

42
Q

X (and no Y)

A

Turner Syndrome: phenotypicaly female.

Animal Biology (23 decks)

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