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Biology 121 > Questions #9 > Flashcards

Questions #9 Flashcards

October 24 - October 31

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1
Q

What is the exception to the third postulate of cell theory: all cells arise by division?

A

Fertilization requires the union of 2 cells to make one.

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2
Q

Why is sexual reproduction so important for the evolutionary success of eukaryotes?

A

It increases the genetic diversity.

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3
Q

Why is meiosis necessary?

A

Reduces chromosome number in gametes.

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4
Q

What are gem-line cells, and what are somatic cells?

A

gem-line cells=2n cells that will undergo meiosis to produce gametes somatic=non reproductive cells.

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5
Q

What is synapsis, and what is crossing over?

A
  • synapse happens at prophase of meiosis I. It refers to the homologous chromosomes coming close together.
  • crossing over trades DNA between homologous and the result is genetic recombination and variation.
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6
Q

What is genetic recombination

A

the production of offspring with combinations of traits differing from either parent

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7
Q

What are chiasmata?

A

Sites where crossing over has occurred.

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8
Q

What holds the tetrads together during metaphase I?

A

chiasmata

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9
Q

Why does independent assortment occur?

A

One homologue comes from the mother and one from the father. When homologous chromosomes separate in meiosis I chance determines which direction the mother or father homologue go.

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10
Q

How is the chromosome number halved during meiosis?

A

tetrads line up at metaphase 1 and the microtubules attach to the kinetochores on the outside and pull them apart

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11
Q

What is the stage between divisions 1 and 2 of meiosis?

A

interkinesis

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12
Q

Why is division 2 necessary?

A

to separate sister chromatids

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13
Q

What are the four main differences between meiosis and mitosis?

A
  1. synapsis and crossing over in prophase 1
  2. tetrads of chromatids compared of homologous pairs joined by chiasmata on metaphase 1 plate
  3. separations of homologs rather than chromatids at anaphase 1
  4. interkinesis: no S between meiosis 1 and meiosis 2
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14
Q

How is genetic variation introduced by sexual reproduction?

A
  • random fertilization
  • crossing over
  • independent assortment
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15
Q

What is parthenogenesis?

A

unfertilized eggs grow into an individual

ex. male bees in 1N (haploid)

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16
Q

in domestic turkeys viable offspring are sometimes produced from unfertilized eggs. these offspring are diploid, like their mother, what defect in meiosis could give rise to diploid eggs

A

offspring from unfertilized eggs are diploid because homologues fail to separate at Meiosis 1 (nondisjunction)

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17
Q

Down syndrome in humans is caused by having 3 copies of chromosome 21. What defect in meiosis could cause Down’s syndrome?

A

caused by inheritance of third number 21 chromosome, failed to separate

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18
Q

What are the current hypotheses for origin of sex?

A

(enormous amount of genetic variation permits rapid adaptation)

  1. certain kinds of DNA damage can only be repaired using homologous chromosome as template (only way for a haploid to get a homologue is to fuse with another haploid)
  2. contagion-viral infection; can rapidly spread if fuses with related cell and cross over
  3. get ride of parasites
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19
Q

What are the current hypotheses for the advantage of being diploid?

A

1.have a spare good copy of each gene and a spare bad copy of each gene
“red queen”- good to store bad genes until environment changes to where they are useful
2. Miller’s ratchet: diploids can lose bad genes more easily than haploids can

What

20
Q

What was the major difference between Mendel’s model and earlier notions of inheritance?

A

first quantitative study

21
Q

What is a model and what is a model organism?

A

model=comparison standard

model organism=used to infer things about all organisms

22
Q

What is a hybrid?

A

results from the mating of dissimilar parents, offspring are different from the parents

23
Q

What are the five assumptions of Mendel’s model of inheritance?

A
  1. parents transmit genes that provide information about characters
  2. each individual contains 2 alleles for each character
  3. not all copies of a gene are identical
  4. alleles from each parent segregate during gamete production
  5. presence of a gene doesn’t assure that you’ll see its expression
24
Q

What are alleles?

A

Different forms of a genes

25
Q

What is the difference between dominant and recessive alleles?

A

dominant is displayed over the recessive

26
Q

What do homozygous and heterozygous mean?

A 
homozygous = 2 of the same letters (BB or bb)
heterozygous = 2 different letters (Bb)
27
Q

What is the difference between genotypes and phenotypes?

A

genotype is the alleles they have and phenotype is the trait that is displayed

28
Q

Why do you see 3:1 segregation of phenotypes when you self-cross the F1 generation of a monohybrid cross involving a dominant and a recessive allele?

A

three of them will have a dominant allele

29
Q

Why do you see 1:1 segregation of phenotypes when you test cross the F1 generation of a monohybrid cross involving a dominant and recessive allele?

A

If it has a recessive allele and is crossed with a homozygous recessive, the offspring will express the recessive trait

30
Q

What is the addition rule of probabilities?

A

probability of 2 mutually exclusive events in sum of their individual probabilities (or = +)

31
Q

What is the multiplication rule of probabilities

A

probability of 2 independent events occurring simultaneously is equal to the product of each of their probabilities (and = x)

32
Q

If you roll a pair of dice, are you more likely to roll a six or a nine?

A

six

33
Q

What are Mendel’s Laws of Inheritance?

A

law of segregation=alternate forms of a trait are encoded by discreet alleles, one from dad. They will segregate during gamete formation, each gamete has equal probability of getting either allele law of independent assortment=genes located on different chromosomes assort independently of one another during meiosis

34
Q

How does meiosis explain Mendel’s laws of segregation and independent assortment?

A

metaphase 1: random orientation of tetrads on metaphase plate
anaphase 1: homologs separate
anaphase 2: chromatids separate

35
Q

in cats hair length and hair color are specified by unlinked genes. Short hair is dominate over long, and black is dominant over brown. What would the F1 progeny of a cross between a true-breed black cat with short hair and a brown cat with long hair look like? what ratio of phenotypes would you observe in the F2 generation

A

9:3:3:1

36
Q

What are seven complications which make it difficult to figure out patterns of inheritance?

A
  1. most genes have more than 2 alleles and those alleles interact in complicated ways
  2. incomplete dominance
  3. gene interactions (epistasis)
  4. continuous variation
  5. pleiotropy
  6. environmental effects
  7. sex linkage
37
Q

Why are there 4 blood types given there are 3 alleles for the I gene?

A

the A and B can be co dominant

38
Q

Why can people of O blood type give blood to anyone, but only receive O type blood?

A

they don’t have any of the proteins so the antibodies don’t attack it but their antibodies will attack the proteins from the others

39
Q

Why do women who are Rh- need to worry about their husbands blood type?

A

baby may be Rh+, mom is Rh- the mom’s immune system will produce Rh antibodies will produce Rh antibodies against baby’s red blood cells

40
Q

Why do some genes show epistasis?

A

many genes interact sequentially because their products work in pathways

ex. labrador coat color
one gene for pigment
one gene for color deposition
3/4 (12/16), 3/16, 1/16- missing a 3/16

41
Q

What is the difference between incomplete dominance and codominance

A

codominance is when both alleles of a pair are expressed equally (AB type)

incomplete dominance is when there’s an intermediate phenotype (redxwhite=pink)

42
Q

What is the difference between quantitative and qualitative characters?

A

qualitative cannot be expressed in numbers

43
Q

why do Siamese cats have darker fur on the tips of their ears and the end of their tails

A

pigment enzyme is heat sensitive, in warmer areas of the body enzyme is denatured and white fur results

44
Q

What does pleiotropy mean?

A

What does pleiotropy mean?

45
Q

In the pedigree analysis, what does a circle with a dot in it mean?

A

female that is a carrier

46
Q

What did the three patients in the karyotyping analysis have in common

A

they were all trisomic

47
Q

What did you do in the princess and the pea exercise

A

figured out how to breed 25 wrinkled peas before you run out of money

Biology 121 (9 decks)

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