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BIO311D: Biology > GENETICS AND INHERITANCE > Flashcards

GENETICS AND INHERITANCE Flashcards

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1
Q

What is a gene?

A

A gene is a specific sequence of nucleotides in DNA which codes for a specific trait

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2
Q

What is an allele?

A

An allele is a version of a gene

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3
Q

What is a genotype?

A

A genotype is all the alleles of an organism

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4
Q

What is a phenotype?

A

A phenotype is the physical expresssion of a gene (may not always be visible)

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5
Q

What does it mean to be homozygous?

A

Homozygous organism’s have identical alleles

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6
Q

What does it mean to be heterozygous?

A

Heterozygous organisms have different alleles

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7
Q

What is a dominant allele?

A

A dominant allele is an expressed trait

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8
Q

What is a recessive allele?

A

A recessive allele is a nonexpressed trait, but it still present

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9
Q

What does it mean to be monohybrid?

A

Monohybrid means heterozygous for 1 trait

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10
Q

What does it mean to be dihybrid?

A

Dihybrid means heterozygous for 2 traits

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11
Q

What is the “blending” hypothesis?

A

The “blending” hypothesis states that genetic material contributed by 2 parents mixes, just as blue paint mixes with yellow paint to make green

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12
Q

What does the “blending” hypothesis predict?

A

Over many generations, a freely mating population will give rise to a uniform population of individuals

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13
Q

What flaws do the “blending” hypothesis have?

A

It fails to explain how traits can reappear after they’ve skipped a generation

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14
Q

What is the “particulate” hypothesis?

A

The “particulate” hypothesis states that parents pass discrete heritable units called genes which retain their separate identities in offspring. A collection of genes is like a deck of cards and can be shuffles and passed along in undiluted forms from generation to generation

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15
Q

What 2 laws did Mendel derive?

A
  1. Law of Segregation
  2. Law of Independent Assortment
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16
Q

What does the Law of Segregation state?

A

The Law of Segregation states that 2 alleles for a heritable trait segregate during gamete formation and end up in different gametes, and can be explained by the segregation of homologous chromosomes during meiosis

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17
Q

What does the Law of Independent Assortment state?

A

The Law of Independent Assortment states that 2+ genes assort independently during gemete formation, that is, each pair of alleles segregates independently of any other pair of alleles. Only works for genes located on different chromosomes or those that are very far apart on the same chromosome

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18
Q

What model explains the 3:1 inheritance pattern seen across the F2 generation?

A
  1. Alternate versions of genes (alleles) account for variations in inherited characteristics
  2. For each character, an organism inherits 2 copies of a gene (1 from each parent)
  3. If 2 alleles on a locus differ, the dominant allele determines the organism’s appearance while the other has no noticible effects
  4. Law of Segregation
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19
Q

What is a testcross?

A

A testcross is used to reveal the genotype of an organism by breeding an organism of an unknown genotype with a recessive homozygote; any offspring with recessive phenotype means the unknown genotype must be heterozygous

RR x rr = 100% Rr

Rr x rr = 1:1 of Rr:rr

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20
Q

What is the phenotypic ratio for a monohybrid cross?

A

3:1

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21
Q

What is the phenotypic ratio for a dihybrid cross?

A

9:3:3:1

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22
Q

What is the multiplication rule?

A

The multiplication rule calculates the probability that 2+ individual events will occur together (AND)

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23
Q

What is the addition rule?

A

The addition rule calculate the probability that 1 of 2+ exclusive events will occur (OR)

24
Q

What are the different inheritance patterns?

A
  1. Complete dominance
  2. Incomplete dominance
  3. Multiple alleles
  4. Pleiotropy
  5. Epistasis
  6. Polygenic inheritance
  7. Multifactoral
25
Q

What is complete dominance?

A

Complete dominance is demonstrated by 1 allele in a pair when the F1 offspring always look like 1 of the 2 parental variations

26
Q

What is incomplete dominance?

A

Incomplete dominance is when neither allele is completely dominant, and th F1 hybrids have a phenotype somewhere between those of the 2 parental varieties. The result is a third phenotype which is a combination of the phenotypes of both alleles

27
Q

What is an example of incomplete dominance?

A

Pink snapdragon flowers whose parents are red and white snapdragons

28
Q

What is the phenotypic ratio for incomplete dominance?

A

1:2:1

29
Q

What is multiple allele inheritance?

A

Multiple alleles/codominance is when 3+ alternative forms of a gene (allele) occupy the same locus

30
Q

What is an example of multiple allele inheritance?

A

ABO blood types

31
Q

What is codominance?

A

Codominance is when alleles of a gene pair in a heterozygote are fully expressed

32
Q

What is an example of codominance?

A

Roan cattle (RW - red and white hair present)

33
Q

What is pleitropy inheritance?

A

Pleitropy inheritance is the occurance of multiple phenotypic effects

34
Q

What is an example of pleitropy?

A

Marfan syndrome

35
Q

What is epistasis inheritance?

A

Epistasis inheritance occurs when the phenotypic expression of a gene at one locus alters that of another

36
Q

What is an example of epistasis?

A

Labrador retrievers

For a lab to have brown hair, it has to be bb. For a lab to have black hair, it can be either BB or Bb. However, a second gene determines whether or not the pigment will be deposited in the hair. So if the lab is ee, it will have yellow hair. If it is either EE or Ee, its hair can have color

37
Q

What is the phenotypic ratio for epistasis?

A

9:3:4

38
Q

What is polygenic inheritance?

A

Polygenic inheritance (aka continuous variation) are additive effects of 2+ genes on a single phenotypic character which varies in gradiations along a continuum

39
Q

What is an example of polygenic inheritance?

A
  1. Height
  2. Weight
  3. Eye color
  4. Skin color
40
Q

How is polygenic inheritance expressed on a graph?

A

In a bell-curve

41
Q

What is multifactoral inheritance?

A

Multifactoral inheritance is when many factors, both genetic and environmental, collectively influence phenotype

42
Q

What is an example of multifactoral inheritance?

A
  1. Siamese cats
  2. Himalayan rabbits
43
Q

How to read a pedigree?

A
  1. Square = male
  2. Circle = female
  3. Diamond = unknown
  4. Filled in = afflicted
  5. Empty = not afflicted
  6. Half filled = carrier (without symptmoms)
44
Q

Which parent determines the child’s sex?

A

The father determines the sex of the child. Each egg receives an X chromosome while half of the sperm cells receives an X chromosome and the others a Y

In order for the embryo to become a male, there neds to be a gene on the Y chromosome called the SRY (sex-determining region of Y) which aids in the development of testes

45
Q

What is the inheritance pattern of X-linked genes?

A
  1. Fathers pass X-linked alleles only to their daughters
  2. Mothers pass X-linked alleles to both their sons and daughters
46
Q

Why will females express the phenotype only if she is homozygous for what allele?

A

Because X-linked traits are due to recessive alleles, so even if she is heterozygous, the trait will be overshadowed by the dominant gene

47
Q

Why do more males than females have X-linked recessive disorders?

A

Because males are hemizygous, meaning they only have 1 locus and will express that trait in which they receive from their mother

48
Q

What is X inactivation in females?

A

While females are XX, 1 X chromosome in each cell is inactivated during early embryonic development so the cells of both males and females have the same effective dose of most X-linked genes

49
Q

What is the result of X inactivation?

A

A barr body is the condensed form of the inactivated X in each cell of a female which lies along the inside of the nuclear envelope

50
Q

What are examples of X-linked disorders caused by recessive alleles on the X chromosome?

A
  1. Color blindness
  2. Duchenne muscular dystrophy
  3. Hemophilia
  4. Androgen insensitivity syndrome
51
Q

What are examples of recessive inherited disorders?

A
  1. Cystic fibrosis
  2. Sickle-cell anemia
  3. Tay-Sachs disease
  4. Albinism
  5. Phenylketonuria
52
Q

What are examples of dominant inherited disorders?

A
  1. Achondroplasia (dwarfism)
  2. Polydactyl
  3. Huntington disease
53
Q

What are examples of sex-linked recessive disorders?

A
  1. Color blindness
  2. Hemophilia
  3. Anhydrotic dysplasia
  4. Muscular dystrophies
54
Q

What is genomic imprinting?

A

Genomic imprinting is when the phenotype depends on which parent passed along the allele for a few mammalian traits

55
Q

What causes genomic imprinting?

A

Genomic imprinting is due to the addition of a methyl (-CH3) group to C- nucleotides and chemical histone changes to silence a given gene

56
Q

Why is methylation reversible in ovarian and testicular cells?

A

Because genomic imprinting depends on the sex of the parent transmiting the gene

57
Q

What is the inheritance pattern for organelle genes?

A

Extracellular/cytoplasmic genes are found in organelles and are inherited maternally because the zygote’s cytoplasm comes from the egg

BIO311D: Biology (14 decks)

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