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Genetics > Test #4 Review > Flashcards

Test #4 Review Flashcards

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1
Q

What is a gene?

A

An inherited factor (encoded in the DNA) that helps determine a characteristic.

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2
Q

What is an allele?

A

One of two or more alternative forms of a gene

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3
Q

What is a locus?

A

Specific place on a chromosome occupied by an allele

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4
Q

What is a genotype?

A

set of alleles possessed by an individual organism

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5
Q

What is a heterozygote?

A

An individual organism possessing two different alleles at a locus

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6
Q

What is a homozygote?

A

An individual organism possessing two of the same alleles at a locus

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7
Q

What is a phenotype or trait?

A

The appearance or manifestation of a characteristic

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8
Q

What is a characteristic or character?

A

An attribute or feature possessed by an organism

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9
Q

What is Mendles’ Monohybrid cross?

A

cross between two parents that differ in a single characteristic

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10
Q

What was Mendles’ first conclusion?

A

One character is encoded by two genetic factors

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11
Q

What was Mendles’ second conclusion?

A

Two genetic factors (alleles) separate when gametes are formed

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12
Q

What was Mendles’ third conclusion?

A

The concept of dominant and recessive traits

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13
Q

What was Mendles’ fourth conclusion?

A

Two alleles separate with equal probability into gametes

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14
Q

What is true breeding?

A

only 1 type of allele present

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15
Q

What is the principle of segregation (Mendel’s 1st law)?

A

Each individual diploid organism possesses two alleles for any particular characteristic. These two alleles segregate when gametes are formed, and one allele goes into each gamete.

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16
Q

What is the principle of independent assortment (2nd Law)?

A

Alleles at different loci separate independently

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17
Q

What is the concept of dominance?

A

When two different alleles are present in a genotype, only the trait encoded by one of them-the “dominant” allele - is observed in the phenotype

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18
Q

What is probability?

A

the likelihood of the occurrence of a particular event

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19
Q

What is used to reveal the principle of independent assortment?

A

dihybrid crosses

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20
Q

What is a pedigree?

A

pictorial representation of a family history; a family tree that outlines the inheritance of one or more characteristics

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21
Q

What is a proband?

A

the person from whom the pedigree is initiated

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22
Q

Why do male and female gametes differ in size?

A

The egg has all of the organelles and the sperm just carries a nucleus with DNA

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23
Q

What are the two sexual phenotypes?

A

Male and Female

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24
Q

What are autosomes and how many pairs do we have?

A

non-sex chromosomes and 22 pairs

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25
Q

Where are X and Y chromosome homologous?

A

end regions/ pseudoautosomal regions

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26
Q

What is the phenotype and characteristics of someone with XO?

A

Turner syndrome
- female traits, short, low hairline, broad chest, neck folds

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27
Q

What is the phenotype and characteristics of someone with XXY, XXYY, or XXXY?

A

Klinefelter syndrome
- Male traits, tall, small testes, reduced facial hair and pubic hair.

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28
Q

What is the phenotype and characteristics of someone with XXX, XXXX, or XXXXX?

A

Poly-X Females
- Female traits, tall and thin

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29
Q

What is the phenotype and characteristics of someone with XYY.

A

XYY Males
- male traits, tall

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30
Q

What is the role of the X chromosome?

A

The X chromosome contains genetic information essential for both sexes; at least one copy of an X is required.

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31
Q

What arrangement of chromosomes determines male or female?

A

XX- female
XY- male
- absence of Y results in a female phenotype
- one X chromosome is required for development

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32
Q

What is the SRY?

A

(Sex determining region of the Y chromosome)

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33
Q

How can there be a XY female?

A

This can happen if there is a mutation on the SRY gene on the Y chromosome and testosterone production never occurs.

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34
Q

How can there be a XX male?

A

This can occur if a X chromosome contains the SRY gene.

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35
Q

What does the formation of reproductive structure depend on?

A
  • gene action
  • gene and cell interaction within the embryo
  • interactions with other embryos in the uterus
  • interactions with the maternal environment
36
Q

What are the three levels of sexual determination?

A
  • chromosomal sex
  • gonadal sex
  • phenotypic sex
37
Q

When is the embryo neither male nor female?

A

First 7-8 weeks, two undifferentiated gonads

38
Q

What can alternative pathways in gene expression cause?

A

intermediates

39
Q

When does sexual differentiation begin?

A

week 8

40
Q

What does the SRY gene do?

A
  • sex determining region of the Y chromosome
  • encodes a transcription factor
  • transcription factors turn on many other genes
  • starts testosterone production
41
Q

What are the two hormones that affect male pattern development?

A

testosterone and MIH

42
Q

What is testosterone?

A
  • steroid hormone produced by the testis
  • male sex hormone
  • maintains development of Wolffian duct system
43
Q

What does MIH do?

A

Mullerian Inhibiting Hormone
- hormone produced by developing testis that causes breakdown of Mullerian (female) ducts in the embryo

44
Q

What are the requirements and characteristics of female development?

A
  • Requires the absence of the Y chromosome
  • Embryonic gonad develops as an ovary
  • In the absence of testosterone, the Wolffian duct system degenerates
  • In the absence of MIH, the Müllerian duct system forms female reproductive system
45
Q

What is androgen insensitivity?

A

A mutation in the androgen receptor gene (AR) causes XY males to become phenotypic females
- testosterone is produced, but no testosterone receptors so cells develop as female

46
Q

What are characteristic of Androgen Insensitivity?

A
  • No testosterone receptor, but MIH still made and degrades female reproductive system
  • Male development not started
  • XY
  • External female development with no functioning internal reproductive organs
47
Q

Y- Linked characteristics

A
  • only present in males
  • All male offspring exhibit the trait
  • Y chromosome lost DNA over time
  • Important for sex determination is SRY
48
Q

What is dosage compensation?

A

the amount of protein produced by X-linked genes after randomly inactivated X- chromosomes

49
Q

What is Random X - Chromosome inactivation?

A

One X chromosome turns to heterochromatin and turn off that X during development.

50
Q

What are Barr bodies?

A

Hypercondensed X-Chromsomes

51
Q

What does LncRNA do?

A

winds itself around X chromosomes to shut is down.

52
Q

What would be required for a male calico cat?

A

XXY

53
Q

How many Barr bodies do a male with XXXYY chromosomes have in each of his cells?

A
  • 2 Barr bodies
54
Q

What is complete dominance?

A

Phenotype of the heterozygote is the same as the phenotype of one of the homozygotes.

55
Q

What is incomplete dominance?

A

Phenotype of the heterozygote is intermediate (falls within the range) between the phenotypes of the two homozygotes

56
Q

What is Codominance?

A

Phenotype of the heterozygote includes the phenotypes of both homozygotes.

57
Q

What is penetrance?

A

The percentage of individuals having a particular genotype that express the expected phenotype.

58
Q

What is expressivity?

A

the degree to which a trait is expressed (ex; in polydactyly how many extra fingers)

59
Q

What does a ratio of 2:1 mean?

A

one of the outcomes is lethal

60
Q

Describe multiple alleles.

A

For a given locus, more than two alleles are present within a group of individuals

61
Q

Describe gene interaction.

A

Effects of genes at one locus depend on the presence of genes at other loci.

62
Q

Characteristics of gene interaction.

A
  • genes exhibit independent assortment but do not act independently in their phenotypic expression
  • The products of genes at different loci that interact to produce new phenotypes
63
Q

What is epistasis?

A

One gene masks the effect of another gene.

64
Q

A number of all white cats are crossed and they produce the following types of progeny; 12/16 white, 3/16 black, and 1/16 gray. What is the genotype of the black progeny?

A

A_bb or aaB_

65
Q

What causes this ratio 12:3:1?

A

dominant epistasis (ex: color in squash)

66
Q

What causes 9:3:4 ratio?

A

Recessive epistasis (ex: color in labradors)

67
Q

What are the characteristics of cytoplasmically inherited traits?

A
  1. present in males and females
  2. usually inherited from the maternal parent
  3. reciprocal cross give different results
  4. exhibit extensive phenotypic variation, even within a single family
68
Q

What is epigenetics?

A

phenomena due to alterations to DNA that do not include change in the base sequence; often affect the way in which the DNA sequences are expressed

69
Q

What is genomic imprinting?

A

differential expression of genetic material depending on whether it is inherited from the male or female parent.

70
Q

sex linked characteristics

A

genes located on the sex chromosome

71
Q

sex influenced characteristics

A

autosomal genes that are more readily expressed in one sex

72
Q

sex-limited characteristic

A

autosomal genes who expression is limited to one sex

73
Q

genetic maternal effect

A

nuclear genotype of the maternal parent

74
Q

cytoplasmic inheritance

A

cytoplasm genes, which are usually inherited from only one parent

75
Q

genomic imprinting

A

Genes whose expression is affected by the sex of the transmitting parent

76
Q

Discontinuous characteristics

A

relatively few phenotypes

77
Q

continuous characteristics

A

continuous distribution of phenotypes; occurs when genes at many loci interact

78
Q

polygenic characteristics

A

characteristics encoded by genes at many loci

79
Q

pleiotropy

A

one gene affects multiple characteristics

80
Q

What causes a 1:2:1 ratio?

A

incomplete or codominance

81
Q

What causes a 9:3:4 ratio?

A

epistasis (weird ratios that equal 16)

82
Q

Describe epistasis.

A

two genes working in a biochemical pathway together

83
Q

What is required for typical male development?

A
  • Y chromosome
  • SRY gene
  • MIH
  • Testosterone
  • Duct system
84
Q

Explain complete dominance using dosage.

A

Complete dominance occurs because on dose of the proteins of the heterozygous genotype is the same phenotype as the homozygous genotype.

85
Q

Explain incomplete dominance using dosage.

A

Incomplete dominance occurs because one dose of the heterozygous genotype doesn’t result in the same phenotype as the homozygous dominant due do a lack of protein dosage and leads to an intermediate phenotype.

86
Q

Explain codominance using dosage.

A

codominance occurs when one dose of each two different alleles is expressed and produces a new phenotype.

87
Q

How can we determine if a gene is incomplete or codominant?

A

biochemical process to determine which one/ can’t use genotype

Genetics (14 decks)

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