Chapter 6: Classical Genetics Flashcards Preview

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Flashcards in Chapter 6: Classical Genetics Deck (100):
1

Who's the father of modern genetics?

Gregor mendel is the father of modern genetics

2

What did Gregor Mendel do?

medal bred peas in order to study patterns of heredity

3

What did Mendel discover from his work with pea plants?

Mendel's pea discoveries:
1. law of dominance
2. law of segregation
3. law of independent assortment

4

What's the law of dominance?

the law of dominance says that when two oppositely homozygous (e.g. TT and tt) organisms are crossed, the offspring will be hybrid but will only exhibit the dominant trait.

5

What's a hybrid?

a hybrid carries two (2) different alleles for the same gene (e.g. Tt or Yy)

6

What's the law of segregation?

the law of segregation says that when gametes form, the two traits carried by each parent SEPARATE.
E.g. Tt -> T and t gametes

7

What's a gamete?

a gamete is one ALLELE
e.g. t or y

8

What's a monohybrid cross?

a monohybrid cross is between to organisms that are hybrid for a single trait.
ex. Tt and Tt

9

examples of a monohybrid cross?

crossing Tt and Tt, or Yy and Yy

10

What's the phenotype?

what the organisms looks like
-PHysical appearance

11

What's the genotype?

the type of genes the organism has.
-GENes

12

What's the phenotype ratio for a monohybrid cross?

phenotype ratio: three (3) look dominant, one (1) looks recessive
3:1

13

What's the genotype ratio for a monohybrid cross?

genotype ratio: 1:2:1
- one (1) is homozygous dominant (TT)
- two (2) are heterozygous (Tt)
- one (1) is homozygous recessive (tt)

14

What's the purpose of a test cross?

the purpose of a test cross is to determine whether an individual organism showing the dominant trait is homozygous dominant or heterozygous

15

How do you perform a test cross?

to perform a test cross, cross the unknown genotype with a HOMOZYGOUS RECESSIVE individual.

16

What's the law of independent assortment?

The law of independent assortment says that when gametes form, the genes for one trait (such as T or t) are not inherited with another gene from the same parent (such as Y or y).

17

What does the law of independent assortment apply to?

the law of independent assortment applies to DIHYBRID crosses!

18

What are the parents if you do a cross and the phenotype ratio of the offspring is 3:1?

the parents are HYBRIDS for the trait!

19

In a cross with two or more different genes, what determines how the different alleles are inherited?
(e.g. TtYY x ttYy)

The only factor that determines how the different alleles are inherited is how the HOMOLOGOUS PAIRS line up in METAPHASE of meiosis 1, which is completely RANDOM.

20

What's a dihybrid cross?

a dihybrid cross is a cross between two organisms that are HYBRID for TWO (2) different traits!

21

What are the parents if you do a cross and the phenotype ratio of the offspring is 1:1?

one parent is a HYBRID, and one parents is HOMOZYGOUS RECESSIVE.
B b
b Bb bb
b Bb bb

22

What's the phenotype ratio for a DIHYBRID cross?

phenotype ratio: 9:3:3:1
1. nine (9) will be completely dominant for both traits (AB)
2. three (3) will be dominant for one trait, and recessive for the other (Ab)
3. three (3) will be dominant for one trait, and recessive for the other (aB)
4. one (1) will be completely recessive for both traits. (ab)

23

What's incomplete dominance?

when both traits BLEND together
e.g. crossing a red snapdragon and white snapdragon flower gets you a pink snapdragon

24

What's codominance?

codominance is when BOTH TRAITS are expressed equally

25

What's MULTIPLE ALLELES?

multiple alleles is when there are more than two allelic forms of a gene.

26

example of multiple alleles?

blood type

27

What alleles determine blood type?

it's determined by A, B, and O.

28

How are the blood type alleles written?

1. A is I^A
2. B is I^B
3. O is i

29

What alleles make blood type A?

A:
1. AA
2. Ai

30

What alleles make blood type B?

B:
1. BB
2. Bi

31

What alleles make blood type I?

I:
1. ii

32

What're polygenic traits?

polygenic traits are caused by several separate genes that vary along a continuum blending together.

33

example of polygenic inheritance?

when two parents that are short carry more genes for shortness than for tallness, but their child inherits mostly the tall genes and will be taller than their parents.

34

What does polygenic inheritance result in?

polygenic inheritance results in a BELL-SHAPED curve in an ENTIRE POPULATION

35

What're sex-linked genes?

genes located on either sex chromosome

36

How many genes are on the X chromosome or are X-linked?

there are one-thousand and one-hundred genes (1,100) on the X chromosome

37

What type of sex-linked traits are more common?

RECESSIVE sex-linked traits are more COMMON.

38

Polygenic inheritance results in ____.

polygenic inheritance results in a BELL-SHAPED curve in an ENTIRE POPULATION

39

What're the male sex chromosomes?

XY

40

____ sex-linked traits are more common.

RECESSIVE sex-linked traits are more COMMON.

41

What're the female sex chromosomes?

XX

42

How many genes are on the Y chromosome or are Y-linked?

there are seventy-eight (78) genes on the Y chromosome

43

Which sex suffers from sex-linked conditions more?

MALES suffer from sex-linked conditions more than women.

44

What're some examples of RECESSIVE sex-linked traits? (very important)

recessive sex-linked traits include:
1. color blindness
2. hemophilia

45

Can sons inherit a X-linked trait from their father?

NO, they can only inherit the Y chromosome from their father, or else they'll be female (lol)

46

What chance does a son have of inheriting an X-linked trait from his mother who heterozygous for the trait?

50%

47

Can males be carriers for X-linked traits?

NO! they either express the trait if they have it at all or DON'T

48

Why can't males be carriers for X-linked traits?

because they only have ONE (1) X chromosome!
- so they either express the trait if they have it at all or DON'T.

49

What factors can influence your phenotype?

1. your environment
- e.g. intelligence
2. your sex.
- e.g. males are more likely to bald.

50

What's a sex-influenced trait?

a trait that's influenced by your sex

51

What's an example of a sex-influenced trait?

male-pattern baldness

52

For karyotypes, when do scientists prepare and photograph the chromosomes?

scientists prepare and photograph the chromosomes during METAPHASE of mitosis when they're fully condensed.

53

How many chromosomes do humans have?

humans have FOURTY-SIX (46) chromosomes

54

In a pedigree, what represents females?

In a pedigree, CIRCLES represent females!

55

In a pedigree, what represents people that CARRY a trait?

In a pedigree, a HALF shaded-in shape represents people that CARRY a trait.

56

How many autosomes do humans have?

humans have FOURTY-FOUR (44) autosomes

57

In a pedigree, what represents people that EXHIBIT a trait?

In a pedigree, a COMPLETELY shaded-in shape represents people that EXHIBIT a trait.

58

In a pedigree, what represents males?

In a pedigree, SQUARES represent males!

59

When are chromosomes fully condensed?

chromosomes are fully condensed during METAPHASE of mitosis.

60

How many sex chromosomes do humans have?

humans have TWO (2) sex chromosomes

61

What are the types of MUTATIONS?

the types of mutations are
1. GENE mutations
2. CHROMOSOME mutations.

62

What causes gene mutations?

a change in the DNA sequence causes gene mutations

63

What are chromosome mutations?

changes in the STRUCTURE of the chromosomes.

64

Can you see chromosome mutations?

YES, you can see chromosome mutations using a LIGHT microscope!

65

What's nondisjunction?

nondisjunction is when HOMOLOGOUS chromosomes fail to separate correctly during meiosis.

66

What happens because of nondisjunction?

nondisjunction causes one gamete to receive TWO (2) homologous, and one gamete to receive ZERO (0).

67

What's ANEUPLOIDY?

aneuploidy is when you have any ABNORMAL CHROMOSOME condition.

68

What's trisomy?

trisomy is when you have three (3) copies of one type of chromosome, instead of the normal two (2).

69

example of trisomy?

down syndrome

70

What's Down syndrome?

when you have three (3) number 21 (#21) chromosomes.

71

What's a triploid?

a triploid cell is a cell with an extra set of chromosomes (3n).

72

What's a polyploid?

a polyploid cell is a cell with more than three (3) sets of chromosomes.

73

What're the types of chromosomal mutations?

types of chromosomal mutations:
1. deletion
2. inversion
3. translation
4. polyploidy
5. nondisjunction

74

What's the chromosomal mutation called DELETION?

deletion is when part of the chromosome is lost during cell division

75

What's the chromosomal mutation called INVERSION?

inversion is when a chromosomal fragment reattaches to its original chromosome but in the REVERSE orientation.

76

What's the chromosomal mutation called TRANSLOCATION?

translocation is when a chromosome fragment attaches to a non-homologous chromosome.

77

What's the chromosomal mutation called POLYPLOIDY?

polyploidy is when a cell or organism has extra sets of CHROMOSOMES.

78

how is phenylketonuria inherited?

phenylketonuria is AUTOSOMAL RECESSIVE.

79

What is phenylketonuria?

phenylketonuria is when you can't break down the AMINO ACID phenylalanine.

80

If you have phenylketonuria and eat phenylketonuria, what happens?

you become retarded
(yes I'm being real here).

81

how is cystic fibrosis inherited?

cystic fibrosis is AUTOSOMAL RECESSIVE

82

What is cystic fibrosis?

cystic fibrosis is when EXTRACELLULAR FLUID builds up in your body.

83

What's Tay-Sachs disease?

Tay-Sachs disease is when you lack an enzyme that breaks down lipids necessary for the brain to function normally.

84

How is Tay-Sachs disease inherited?

Tay-Sachs disease is AUTOSOMAL RECESSIVE.

85

What's Huntington's disease?

Huntington's disease is when your nervous system begins breaking down early, causing you to die earlier

86

how is Huntington's disease inherited?

Huntington's disease is AUTOSOMAL DOMINANT.

87

What's hemophilia?

hemophilia is when you lack one or more proteins necessary for your blood to clot.

88

how is hemophilia inherited?

hemophilia is X-linked RECESSIVE.

89

What's color blindness?

it's when you can't see the colors RED and GREEN.

90

How is color blindness inherited?

color blindness is X-linked RECESSIVE.

91

What're some examples of chromosomal disorders?

chromosomal disorders:
1. down syndrome
2. klinefelter's syndrome.

92

What's the genetic definition of Down syndrome?

Down syndrome is when you have 47 chromosomes. you have three (3) of chromosome 21, instead of the usual two (2)

93

What're the physical characteristics of someone with Down syndrome?

Down syndrome:
1. mental retardation
2. prone to develop Alzheimer's and leukemia

94

What's the genetic definition of klinefelter's syndrome?

klinefelter's syndrome is when a male has an extra X chromosome.
- so their sex chromosomes are XXY

95

What're the physical characteristics of someone with klinefelter's syndrome?

klinefelter's syndrome:
1. they have male genitals
2. but the testes are abnormally small
3. and they can't have babies. (they're sterile).

96

Which type of cross best represents Mendel's Law of Segregation?

the MONOHYBRID cross best represents Mendel's Law of Segregation.

97

A hybrid red flower (Rr) is crossed with a white flower. what percentage of the offspring will be red?
a. 0
b. 25
c. 50
d. 75
e. 100

c. 50

98

Which of the following crosses best demonstrates the law of segregation?
a. AA x aa
b. aa x aa
c. Aa x aa
d. Aa x Aa
e. AA x AA

d. Aa x Aa

99

What's the scientific definition of cystic fibrosis?

people with cystic fibrosis have a NONFUNCTIONING gene in certain body cells.

100

How can cystic fibrosis be cured, theoretically?

it can be cured if scientists could replace the nonfunctioning gene with a functioning gene through RECOMBINANT DNA.