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1

Genetic variations is a consequence of _________.

Meiosis (crossing over)

2

How many pairs of chromosomes in human cells?

23 pairs = 46 chromosomes

3

How many possible combinations of chromosomes in one human gamete?

2^23 = 8 million

4

Possible combinations of chromosomes as a consequence of sexual reproduction?

2^23 X 2^23 = 70 trillion

5

Gene

Inherited factor (region of DNA) that helps determine a characteristic

6

Allele

One of two or more alternative forms of a gene.

7

Locus

Specific place on a chromosome occupied by an allele

8

Genotype

Set of alleles possessed by and individual (i.e. Rr, rr, RR)

9

Phenotype

The physical appearance or manifestation of a characteristic

10

Does the phenotype always match the genotype?

No, the genotype does not always match bc of recessive alleles.

Rr = Non-red hair
RR = Non-red hair
rr = Red hair

11

Heterozygote

An indiv organism possessing two diff alleles at a locus

Rr

12

Homozygote

An indiv organism possessing two of same alleles at a locus

RR
rr

13

Characteristic or character

An attribute or feature possessed by an organism

14

What happens during Interphase?

DNA synthesis
Chromosome replication phase

15

In general, what happens during Meiosis I

Separation of homologous chromosome pairs
Reduction of chromosome number by half

16

In general, what happens during Meiosis II?

Separation of sister chromatids (equation all division)

17

Before Meiosis I, is the parents cell haploid of diploid?
After Meiosis I are the daughter cells haploid or diploid?
After Meiosis II?

B4 Meiosis I - Diploid
After Meiosis I - Haploid
After Meiosis II - Haploid

18

How much of DNA in daughter cells after Meiosis I and II compared to parent cell?

Parent - 4x DNA
Meiosis I daughter cells (2) - 2x DNA
Meiosis II daughter cells (4) - 1x DNA

19

1. Diploid cells have ____ chromosomes.
2. Haploid cells have ____ chromosomes.

1. 46
2. 23

20

Homologous pairs of chromosomes

Similar but NOT identical chromosome

Carry same genes in same order, BUT alleles for each trait may be different

21

Centromere function

Point on a chromosome by which it is attached to a spindle fiber during cell division

Binds homologous chromosomes together

22

Chromatid

Either of the two daughter strands of a duplicated chromosome that are joined by a single centromere and separate during cell division to become individual chromosomes

23

Independent centromere = ?
Shared centromere = ?

Independent centromere = chromosome
Shared centromere = sister chromatids

24

Replication of homologous chromosome produces __________.

Sister chromatids

25

Synapsids

Close pairing/binding of homologous chromosome

26

Tetrad

Closely associated four-sister chromatids of two homologous chromosomes

27

How a tetrads significant to genetic variation?

Close association of tetrads with each other cause crossing over/recombination

28

Crossing over

Exchange of genetic material btw homologous chromosomes and results in the shuffling of genes along the chromosome

Matching regions on homologous chromosomes break and then reconnect to the other chromosome

29

What is the significance of crossing over to genetic variation?

Causes unequal exchange of genetic info, producing chromosomes with deleted or duplicated regions

Chromatids held together by the centromere are no longer identical

After meiosis II, Some daughter cells receive chromosomes w/ recombined alleles

Offspring have diff set of alleles and genes than parents do
----> Genetic variation

30

What does meiosis produce?

A. Haploid gametes
B. Diploid gametes
C. Diploid cells
D. Haploid cells

A

31

Can normal separation of chromosomes occur w/o crossing over?

No, crossing over is necessary to the proper separation of chromosomes.

32

What stage(s) of meiosis can crossing over take place

Late Prophase

33

Middle Prophase

Chromosomes begin to condense
Spindle/centrosomes form

34

Late Prophase I

Homologous chromosomes pairs synapse

Nuclear membrane breaks down

Crossing over takes place

35

What can happen to chromosomes in Prophase as a result of stress/loss of nuclear membrane?

Chromosomes can break

Segments lost

36

Metaphase I

Homologous pairs of chromosomes line up along the metaphase plate

37

Anaphase I

Homologous chromosomes separate and move toward oppo poles

38

Telophase I

Chromosomes arrive at the spindle poles

Cytoplasm divides

39

What is different about length of time in Prophase II than time in Prophase I?

Prophase II is much shorter than Prophase I

40

Prophase II

Chromosomes recondense
Nuclear envelope disintegrates

41

Metaphase II

Indiv chromosomes line up along Equatorial/metaphase plate

42

Anaphase II

Sister chromatids separate and toward oppo poles

43

Telophase II

Chromosomes arrive at the spindle poles

Cytoplasm divides

44

Product of Meiosis II

4 haploid gametes

45

Fertilization is fusion of _______ gametes.

Haploid

47

How has high genetic variation in humans been an evolutionary advantage?

Many possible combination of genes

Allow many diff ways for the survival of humans and success in natural selection

Big/strong
Small/smart

48

Crossing over is proportional to ________

Distance

49

Proportion to distance of crossing over allows us to creat what?

A physical map of the chromosome

50

# of possible combinations of chromosomes in gametes depending on how chromosomes align and separate during meiosis I and II?

8

51

What is true about the newly formed cells from meiosis?

A. They are genetically different from one another but are the same genetically as the parent cells
B. They are genetically the same as one another and the parent cells
C. They are genetically the same as one another but are diff genetically from the parent cells
D. They are genetically different from one another and the parent cells

D.

52

Which of the following takes place in meiosis II, but not in meiosis I?

A. Crossing over
B. Contraction of chromosomes
C. Separation of homologous chromosomes
D. Separation of chromatids

D.

53

What is key to behavior of chromosomes in mitosis and meiosis?

Cohesin


54

Cohesin

Protein complex that holds the chromatids together

55

What signals breakdown of cohesin for separation of chromosomes?

Separin

56

Why must Separin signaling be complex?

In meiosis I, Separin must signal Cohesin to breakdown at the chromosome arms to allow pairs of homologous chromosomes to separate but Cohesin must be intact at the centromere

In meisosis II, Separin signals Cohesin to break down at centromeres to allow chromatids to separate.

57

When does meiosis occur in animals?

Spermatogenesis - Male gametes production
Oogenesis - Female gamete production

58

Differences of plant meiosis from animal meiosis

Diff amounts of times in stages of life cycle
Distinct phase of life cycle spent in halpoid state

59

What is the difference btw meiosis in less complex plants and more complex plants?

Less complex - more time haploid
More complex - less time haploid (evolutionarily favored)

60

Stages of spermatogenesis and their ploidy

Spermatogonium (2n)
Primary spermatocyte (2n)
Secondary spermatocyte (n)
Spermatids (n)
Sperm (n)

61

Stages of Oogenesis and their ploidy

Oogonium (2n)
Primary Oocyte (2n)
Secondary Oocyte (n)
Ovum (n)

62

Polar bodies

Formed during Oogenesis from the in completes cytoplasm/organelle separation

Disintegrates

63

Why is ovum larger than the sperm?

Get more DNA from Mom

Get Mitochondrial DNA from Mom but NOT Dad

64

Can horses and donkeys interbreed even though they are diff species and if so how?

Yes, they are close enough genetically that a sperm and egg can complement each other enough to allow for meiosis

65

What is offspring of horse and donkey?
Why is it sterile?

Mule

Sterile bc have odd number of chromosomes
Make unbalanced gametes that do NOT have all genetic info
Non-functional gametes

66

Consequences of improper segregation of chromosomes during meiosis?

Down syndrome - trisomy 21
Klinefelter - XXY

67

Can nondisjunction occur with any chromosome other than chromosome 21?

No, nondisjunction of other chromosomes are fatal and the fetus will not be viable

67

Heredity

Passing on of physical or mental characteristics genetically from one generation to another

67

Heritability

The proportion of total variation btw individuals in a given popul that is due to genetic variation

68

Which would result in red hair?

A. Wild type MC1R gene
B. Heterozygous
C. 1 copy of MC1R amino acid variant
D. 2 copies of MC1R amino acid variant

D.

69

Why does the MC1R with amino acid variants result in red hair?

MC1R encodes the melanocortin 1 receptor

If have one copy of variant MC1R, this reduces receptor efficiency, causing the pathway to shift to pheomelanin production

If have 2 copies, pheomelanin is predominant pigment over enumerating (brown hair), which results in red hair

70

Gene

A locus (or region) of DNA that encodes a functional RNA or protein product

71

Allele

An alternative form of a gene (one member of a pair) that is located at a specific position on a specific chromosome

72

Which amino acid is substituted in the the MC1R protein in red heads?

Cysteine is substituted for and Arginine (R)

73

What other trait does having the two MC1R variants cause?

Sensitivity to anesthetics

74

Why did Mendel choose the traits he chose to study?

Those traits developed a pattern that he could study and create a mathematical description for.

Chosen so that crossing over had no effect on study

75

Mono hybrid cross

Cross btw two parents that differ In a single characteristic

76

Genotype:

Phenotype:

Genotype: Genetic constitution of an indiv

Phenotype: Set of observable characteristics of an indiv from the interaction of its genotype with the environment

77

4 Conclusions from monohybrid cross

1: One character is encoded by two genetic factors (alleles)
2: Two alleles separate when gametes are formed
3: The concept of dominant and recessive traits
4: Two alleles separate with equal probability into gametes

78

Homozygous

Heterozygous

Homozygous:
True breeding
Alleles are identical (RR or rr)

Heterozygous:
Pair of diff alleles
One dominant and one recessive (Rr)



79

Principle of segregation (Mendel's First Law)

Each indiv diploid organism possesses two alleles for any particular characteristic and only one is passed to offspring

80

Independent assortment

Alleles segregate independently when gametes are formed

81

The concept of Dominance

When two diff alleles are present in a genotype, only the trait encoded by one of them, the "Dominant" allele,is observed in the phenotype. The other allele is recessive.

82

What type of cross demonstrates the principle of segregation?

Monohybrid cross

83

Chromosome Theory of Inheritance

Inheritance patterns may be generally explained by assuming that genes are located in specific sites on chromosomes

84

Two alleles of a genotype are located on:

A. Sister chromatids
B. Homologous chromosomes
C. Chromosomes
D. Tetrads

B.

85

When do chromosomes replicate?

A. S Phase
B. M phase
C. Replicating phase
D. G1 phase

A.

86

When can crossing over occur?

A. Metaphase I
B. Telophase II
C. Interphase I
D. Prophase I

D.

87

What increases the likelihood of a cross over event occurring?

Increased distance between genes (farther apart)

88

Punnet squares

Used to predict the outcomes of genetic crosses

89

How was the theory of inheritance tested

Back cross - cross F1 generation with Parent

90

If don't know anything about parents genotype what is normally done?

Cross the unknown parent with a homozygous recessive

High probability of seeing recessive phenotype:
- Either 100% recessive phenotype
- Or 50/50

91

If an F1 plant (round seeds, heterozygous) is back crossed to the parent with round seeds (homozygous), what portion of progeny will have wrinkled seeds?

A. 3/4
B. 1/2
C. 1/4
D. O

D.

92

You cross 2 pure breeding rabbit, a male with black fur and a female with tan fur, and all of the F1 bunnies have tan fur.

Which is dominant?
Which is recessive?
Does it matter which parent contributes the dominant trait?

1. Dominant - tan
2. Recessive - black
3. No