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Biology 121 > Sheet 9--Test 3 > Flashcards

Sheet 9--Test 3 Flashcards

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1
Q

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

A

1) Increases Genetic diversity
2) food for evoultion
3) helps eukaryotes evolve rapidly

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2
Q

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

A

Results in more genetic variability

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3
Q

Why is meiosis necessary?

A

Reduces chromosome number in gametes

    • germ line cell 2n undergoes meiosis to get 4 1n cells
  • -gametes are 1n= 23 chromosomes and they have 1 copy of each chromosome and 1 chromatid each
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4
Q

What are germ-line cells?

A

2n cells that will undergo meiosis to produce gametes

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5
Q

What are somatic Cells?

A

body cells (non-reproductive cells)

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6
Q

What is synapsis?

A
  • occurs Prophase 1
  • Homologous chromosomes pair to form a tetrad
  • biggest difference–this does not occur in Mitosis
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7
Q

what is crossing over?

A

inner chromatids “cross over” and exchange genetic information

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8
Q

what is genetic recombination?

A

inner chromatids now have genetic information they did not have before

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9
Q

what are chiasmata?

A

areas where homologous chromosomes join during crossing over– this site remains until anaphase 1

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10
Q

what holds the tetrads together during metaphase 1?

A

Chiasmata

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11
Q

why does independent assortment occur?

A

Metaphase 1
homologous chromosomes line up randomly on metaphase plate. Daughter cells get a random mix of chromosomes from each parent.

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12
Q

how is the chromosome number halved during meiosis?

A

Metaphase 1
tetrads line up on metaphase plate and microtubules attached only to outside kinetochores
- homology with 2 chormatids pulled to each pole during anaphase 1

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13
Q

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

A

Interkinesis

* DNA does not replicate

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14
Q

why is division 2 necessary?

A

Division (Meiosis) 2 is necessary to separate sister chromatids

    • second Meiotic Division resembles Mitosis
  • -results in 4 haploid daughter cells.
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15
Q

what are the four main differences between meiosis and mitosis?

A

Unique Features of Meiosis:

  • synapsis and crossing over during prophase 1
  • tetrads of chromatids composed of homologous pairs joined by chiasmata on metaphase 1 plate.
  • Separation of homologs rather than chromatids at anaphase 1
  • Interkinesis: no “S” between meiosis 1 and meiosis 2
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16
Q

How is genetic variation introduced during Meiosis?

A

1) crossing over (Prophase 1)

2) independent assortment (Metaphase 1)

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17
Q

Which stages of meiosis introduce genetic variation?

A

Crossing over– Prophase 1
Independent assortment– Metaphase 1
Separation of Homologs– Anaphase 1

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18
Q

How is genetic variation introduced by sexual reproduction?

A
    • random fertilization
    • genetic information reshuffled by genetic recombination and independent assortment (meiosis)
  • -sperm + egg –> zygote
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19
Q

What is parthenogenesis?

A

unfertilized eggs grow into an individual

–ex. Male bees are 1N (haploid)

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20
Q

In domestic turkeys viable offspring are sometimes produced from unfertilized eggs. These off spring are diploid, like there mother.

A

offspring from unfertilized eggs are diploid because homologes fail to separate at Meiosis 1

  • -aneuploidy– incorrect # of chromosoems in gametes
  • -vertebrates that develope from unfertilized eggs are female
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21
Q

Down syndrome in human is caused by having 3 copies of chromosome 21. What defect in meiosis could cause down syndrome?

A

Downsyndrome caused by failure of chromosomes #21 to separate correctly during meiosis 1 or meiosis 2

  • -sygote gets 3 copies of #21 instead of 2 copies
  • -pair didnt seperate or chromatids didnt seperate
  • -occurs in anaphase 1 or anaphase 2(chromatids)
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22
Q

What are the current hypothesis for the origin of sex?

A

Enormous amount of genetic variation permits rapid adaption

1) certain kinds of DNA damage can only repaired using homologous chromosomes as template
- —only way for a haploid to get homologue is to fuse with another haploid

2) contagion– viral infection; can rapidly spread if fuses with related cell and cross over
3) get rid of parasites

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23
Q

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

A

1) have a spare good copy of each gene and a bad copy of each gene
- –“red Queen” hypothesis: store bad genes until they are useful to keep up with enviromental change
- —–example- sickle cell anemia–recessive disorder–Aa

2) millers ratchet:
- —diploids can lose bad genes more easily than haploids

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24
Q

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

A

used math model to determine genetics

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25
Q

what is a model?

A

a model is a comparison standard.

–ex. Mendel’s model of inheritance

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26
Q

what is a model organism?

A

Model organisms are used to infer things about all organisms

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27
Q

what is a hybrid?

A

hybrid results from the mating of dissimilar parents; offspring are different from parents

  • -parents must be pure bread
  • – AA x aa = Aa
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28
Q

what are the 5 assumptions of Mendel’s model of inheritance?

A

1) parents transmit genes that provide information about characteristics
2) neach indiviudal contains 2 genes for each character= dominant and recessive
3) not all copies of a gene are identical
4) alleles from each parent segregate during gamete production
5) presence of a gene doesnt assuure that youll see its expression

Aa–> shows dominant trait.

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29
Q

What are alleles?

A

different forms of the same gene
A– dominant allele
a– recessive allele

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30
Q

What is the difference between dominant and recessive alleles?

A

In mendelian genetics each character is determined by 2 alleles:
dominant– A
Recessive– a

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31
Q

What does homozygous mean?

A

2 haploid gametes containing the same allele fuse during fertilization

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32
Q

what does heterozygous mean?

A

2 haploid gametes that contain different alleles.

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33
Q

what is a genotype?

A

total set of alleles that an individual has

–genetic make up

34
Q

what is a phenotype?

A

physical appearance or other observable characteristics which result of alleles expression
==physical expression of gene

35
Q

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

A

F1 generation of a monohybrid cross:
P—AA x aa
Gametes–A—A—a—a
==gametes will have only 1 allele each

F1 generation will have Aa, Aa, Aa, Aa

self cross F1 so we cross Aa and Aa (2 heterozygotes)
F1 gametes–A–a–A–a
==law of segreation= 1 allele per gamete

pundit square= AA, Aa, Aa, aa (3:1) ratio dominant recessive

36
Q

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

A

..

37
Q

What is the addition rule of probabilities?

A

Probability of 2 mutually exclusive events is sum of their individual probabilityes.

  • -see the word OR use this
  • -probability of rolling a 6 OR a 5
38
Q

What is the multiplication rule of probabilities?

A

probabilty of 2 independent events occuring simultaneously is equal to the product of each of their probabilities
–see the word AND

39
Q

what are mendel’s laws of inheritance

A

…

40
Q

How does meiosis explain mendel’s laws of segregation

A

Metaphase 1– random orientation of tetrads on metaphase plate

Anaphase 1– homologs separate

Anaphase 2– chromatids separate

41
Q

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

A

Fertilization requires the union of 2 cells to make one

–sperm + egg –> zygote

42
Q

which of the following produces identical cells?

A

mitosis

43
Q

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

A

..

44
Q

At the end of telophase 2 of meiosis, each of the four resulting cells contains?

A

One full set of chromosomes, each a single chromatid

45
Q

If true breeding dominant yellow seeded plants are crossed with recessive green seeded plants, what will the F2 generation look like?

A

3 yellow: 1 green

46
Q

which state of the cell cycle explains mendel’s law of segregation?

A

Meiotic anaphase 1

47
Q

The usual reason genes assort independently of one another is that

A

they are on different chromosomes

48
Q

Yellow and green are two alleles for seed coat color in peas. Yellow seeded plants might be homozygous or heterozygous. The simplest way to find out is by?

A

crossing with any green seeded plant

49
Q

Let P=purple flowers and p= white where purple is dominant , and T=tall plants and t= dwarf where tall is dominant. of the possible offspring in the dihybrid cross, how many would be white and tall?

A

3/16

50
Q

what type of blood can you give to a person who is type AB?

A

all of these

51
Q

You cross an individual who is wwDd with an individual who is WwDd. what fraction of the offspring will be wwdd?

A

1/8

52
Q

What is law of independent assortment

A

genes located on different chromosomes assort independently of one another during meiosis
–metaphase 1

53
Q

What are the 7 complications which make it difficult to figure out patters of inheritance?

A

1) most genes have more than 2 alleles and those alleles interact in complicated ways

2) incomplete dominance (3 phenotypes)
- —red X white –> pink

3) gene interactions (epistasis)
- -ex. lab retriever color

4) continuous variation (polygenese)
- —ex. human height

5) Pleiotropy- one gene many phenotypes
- –ex.sickle cell anemia

6) enviromental effects
- –ex. siamese cat

7) sex linkage– gene is on the X chromosome. label sex chromosome
- -ex. color blindness

54
Q

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

A

alleles–I^A, I^B, i

each person inherits 2 of them

55
Q

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

A

O blood type (universal donor) has no A or B antigen on RBS–> can be given to anyone
–produce both Anti A and Anti B–can only give this person O

AB is universal receipeant because of no antibodies.

56
Q

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

A

baby may be Rh+

    • moms immune system will produce Rh antibodies against baby’s red blood cells.
  • -condition known as erythroblastosis fetalis
57
Q

Why do some genes show epistasis?

A

many genes interact sequentially because their products work in pathways
A–enzyme 1—> B –Enzyme 2—-> C
ex. labrador coat color.
-one gene for pigment
-one gene for color deposition
-two genes on 2 different chromosomes, if working normally ratio would be 9:3:3:1 but they are reall 3/4,3/16,1/16

58
Q

What is the difference between incomplete dominance and codominance?

A

Codominance– both alleles of a pair expressed equally

  • -ex. AB type blood
  • -ex. cross black horse with white horse offspring has black hair AND white hair

Incomplete dominance– heterozygote has intermediate phenotype as alleles dilute effect of each other

  • -ex. red (RR) X white (ww) = pink (RW)
  • -ex. black bunny X white bunny= grey bunny
59
Q

Qualitative vs quanitiative

A

Qualitative–cannot be expressed in numbers
quanititace– can be expressed in number, quanitiative shows continuous variation
–ex. height

60
Q

why do siamese cats have darker fur on the tips of their ears and end of their tail?

A

pigment enzyme is heat sensitive; warmer area of body, enzyme is denatured and white fur resules
–cooler areas, enzyme active= black fur.

61
Q

what does pleiotropy mean?

A

gene has many phenotypes

ex. sickle cell anemia has many complicated all caused by 1 gene

62
Q

what were the 3 possible crossover types in the gene mapping exercise?

A

between a and b, b and c, or a and c

–computer moving the a to b to c thing around

63
Q

how many possible phenotypes were there, and which ones were recombinant?

A

8 phenotypes, 6 recombinant

  • non- recombinant: +++ and y w min
  • -you can have crossing over +wmin or y++ these are recomb

non recom are what you start with

64
Q

When does synapsis occur?

A

prophase 1

65
Q

does synapsis occur in mitosis, meiosis, or both?

A

Meiosis and NOT mitosis

66
Q

what phase does the chiasmata last until

A

anaphase

67
Q

what forms during synapsis

A

tetrad

68
Q

when does independent assortment occur

A

metaphase 1

69
Q

Does DNA replicate in interkinesis

A

no

70
Q

when are sister chromatids separated?

A

meiosis 2–results in 4 haploid cells

71
Q

what is meiosis 2 similar too?

A

mitosis

72
Q

when does synapsis and crossing over occur?

A

prophase 1

73
Q

when does independent assortment occur?

A

metaphase 1

74
Q

when does the separation of homologs occur?

A

anaphase 1

75
Q

what sex are vertebrates that develop from unfertilized eggs

A

female and diplod

76
Q

why are offspring from unfertilized eggs diploid?

A

homologs fail to separate

77
Q

what is down syndroe caused by?

A

failure of chromosome 21 to separate during meiosis 1 or 2 during anaphase 1 or 2

78
Q

if a gene is present will you see its expression?

A

no, only see dominant

79
Q

when do homologs separate

A

anaphase 1

80
Q

when do chromatids separate

A

anaphase 2

Biology 121 (9 decks)

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