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BIOL 103 > Lecture 9-10 (Quiz 5) > Flashcards

Lecture 9-10 (Quiz 5) Flashcards

1
Q

What are autosomes?

A

Any chromosomes that aren’t sex-linked

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2
Q

How many autosomes/chromosomes do humans have?

A

22 (+ 1 pair of sex chromosomes)

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3
Q

What are male and female chromosmes?

A

XX= Female
XY= Male

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4
Q

What is the difference between haploid and dipploid?

A

Haploid cells contain one set of chromosomes (n), while diploid cells contain two (2n).

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5
Q

What is meiosis and what does it generate?

A

Meiosis is cell division that produces gametes or sex cells. It results in haploid gametes

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6
Q

Does fertilization generate a haploid or diploid zygote?

A

Diploid

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7
Q

What does it mean to be heterogametic?

A

Ability to produce dissimilar gametes. Human males are heterogametic.

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8
Q

What does it mean to be homogametic?

A

Produces only on type of gametes.

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9
Q

Between human somatic cells and human sperm/eggs, which is haploid and which is diploid?

A

Human somatic cells are diploid, while sperms/eggs are haploid.

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10
Q

What is androgen insensitivity syndrome?

A

Patients carry a defective androgen receptor gene on X chromosome. Female phenotype, male genotype (xy)

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11
Q

What are the two steps of sex determination?

A

Primary and secondary sex determination.

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12
Q

What is primary sex determination?

A

Determination of the gonads (Y chromosome specifies testis)

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13
Q

What is secondary sex determination?

A

Affects the bodily phenotype outside the gonads (hormones secreted by testis or ovary).

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14
Q

During sex determination,, despite genotype, what will happen if there is no signalling?

A

Female

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15
Q

What is the default program for sex determination (for humans)?

A

Female

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16
Q

What are non-genetic mechanisms that some organisms determine sex?

A

Temperature, location, population size, sex of others

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17
Q

In drosophila, what determines sex?

A

Like humans, females are XX and males are XY, but the Y chromosome doesn’t determine sex. Rather, the # of X chromosomes determines sex.

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18
Q

What reduction occurs during meiosis?

A

Meiosis reduces the chromosome number from diploid to haploid in gametes?

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19
Q

How do chromosomes assort during meiosis?

A

Each chromosome of the homologous pairs assorts randomly and independently.

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20
Q

How does meiosis generate genetic diversity among the gametes?

A

Crossing over (recombination) if homologous pairs shuffles the parental DNA.

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21
Q

How many divisions occur during meiosis?

A

Meiosis consists of two nuclear divisions, but DNA is replicated only once

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22
Q

What is the difference between mitosis and meiosis?

A

Mitosis generates diploid daughter cells with the same genetic makeup, while meiosis generates haploid daughter cells (sperm + eggs) with genetic diversity.

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23
Q

What are the differences (during division) between mitosis and meiosis)?

A

During meiosis, pairing of homologs during prophase 1 causes recombination (crossover) between two parental chromosomes. Failure to separate the centromeres of the two sister chromatids at the end of metaphase I results in random segregation of the parental chromosomes into the two daughter cells

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24
Q

How does genetic exchange between chromatids happen?

A

During prophase I (meiosis), chiasma (point of contact between two sister chromatids) can cause crossover

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25
Q

What is linkage and how does. it relate to recombination?

A

Genes on the same chromosome are linked and segregate together. Crossover (recombination) can occur multiple times during meiosis I. Recombination diversifies the genetic makeup of the next generation.

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26
Q

What are the possible gametes for 3 traits?

A

Non crossover, single crossover, double crossover

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27
Q

What is recombination?

A

Linearly arranged genes on a chromosome that crossover.

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28
Q

What does the amount of recombination to depend on?

A

Proportional to the physical distance between two loci

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29
Q

What is the unit of recombination?

A

Centimorgans, defined as 1% recombination between two loci

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30
Q

What is nondisjunction?

A

When meiosis goes wrong. A pair of homologous chromosomes (or sister chromatids) fail to separate during cell division. Can occur during both divisions (meiosis I and II)

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31
Q

The gonads in early embryos are _______

A

Bipotential

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32
Q

How does sex reversal come about?

A

Illegitimate recombination between X and Y causes sex reversal. Rare crossover events between X and Y chromosomes during meiosis in male gametes (little piece of Y chromosome stuck on end of X chromosome)

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33
Q

How did scientists isolate the Testis Determining Factor (TDF)?

A

In males with sex-reversal, use DNA with smallest piece of Y to identify TDF.

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34
Q

What is the TDF?

A

The testis determining factor is a transcription fctor called SRY. Sufficient to induce sex reversal (in mice)

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35
Q

Which part of sex determination do hormones control?

A

Secondary sex determination

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36
Q

What is dosage compensation?

A

A need to equalize the expression of X-lines genes

37
Q

What is the purpose of dosage compensation?

A

It ensures an equal expression of genes from the sex chromosomes even though females have two X chromosomes and male have only one

38
Q

What are some mechanisms that equalize expression of X-linked genes?

A

Humans inactivate one of two female X chromosomes; flies double transcription from the single male X chromosomes; worms reduce transcription by half from each female X chromosomes

39
Q

What are pseudoautosomal regions?

A

Parts of human Y chromosome, that contain nucleotide sequences (genes) that are homologous to those on the X, and can thus escape inactivation

40
Q

How does dosage compensation make (female) humans genetic mosaics?

A

Every cell in the body has a different X chromosome inactivated

41
Q

What is the cycle of X chromosome inactivation

A

At different points of development, different X chromosome is inactivated

42
Q

During the two-cell to blastocyst stage, how is the X chromosome inactivated?

A

Selective inactivation of the paternal X chromosome but not he maternal X. Inactivation maintained in extraembryonic tissues.

43
Q

During the inner cell mass stage, how is the X chromosomes inactivated?

A

Reactivation of the paternal X chromosome (Xp). Random inactivation of either Xm or Xp. Inactivation maintained in somatic cells.

44
Q

In primordial germ cells, how are X chromosomes inactivated?

A

Reactivation of inactivated X. Maintained in germ cells.

45
Q

How does random X inactivation occur?

A

Regulated by a region on X called X inactivation center or Xic. Three modes of inactivation steps counting (# of x chromosomes), choice (which to inactivate), and inactivation

46
Q

How does random x inactivation occur?

A

X-inactive specific transcript (xist) is a long non-coding rna that is transcribed from X-linked gene (necessary and sufficient for X inactivation). Transcribed from both, both only bids to one (usually the one that produces more). Once it inactivates an X chromosome, produces Xist while the active does not.

47
Q

What is sex-linked segregation?

A

Certain genes are only on X or Y chromosomes (usually on X chromosome)

48
Q

What is a hormone?

A

Small molecules that generally act at a distance. They are biologically active at very low concentrations, and usually produced in discrete locations. Endocrine hormones circulate through bloodstream. Effect of hormones depends on concentration and receptor population (at target cell)

49
Q

What does tetraploid mean? What does hexaploid mean?

A

Tetraploid = 4 sets of chromosomes
Hexaploid: 6 sets of chromosomes

50
Q

What is chromosome translocation?

A

When a chromosome breaks and piece of it attaches to different chromosome.

51
Q

What is balanced translocation?

A

When no genetic material is lost in the cell during chromosomal translocation (but mutations still occur)

52
Q

What is an unbalanced translocation?

A

When genetic material is lost or increased during chromosomal translocation

53
Q

What does heterozygous mean? What does homozygous mean?

A

Heterozygous means one allele is wild type (+), and the other is mutant (-). Homozygous means both alleles are the same

54
Q

What is the difference between dominant and recessive alleles?

A

Recessive traits only show when they are homozygous, and dominant traits can show whether they are homozygous or heterozygous

55
Q

What is Mendel’s law of segregation?

A

Alleles from different genes assort independently of each other during gametic?

56
Q

Do alleles always sort independently?

A

No. Some alleles dont assort independently.

57
Q

When does linkage happen?

A

When genes dont assort independently?

58
Q

Are genes on the same chromosomes linked?

A

Yes

59
Q

What is crossing over.

A

AKA recombination. Involves reciprocal exchange of chromosome segments between homologs (increases genetic variation)

60
Q

What is a complementation test?

A

A test to examine if two mutations associated with a phenotype affect the same gene or two different genes. Cross two mutants, and if the offspring are wild-type, different genes. If the offspring are still mutant, then the mutations were in the sae gene.

61
Q

How did parabiosis experiments with ob, db, and wild type mice go??

A

db with wt starved wild type to death, db with ob starved ob to death, and ob with wt cured the obesity.

62
Q

What is leptin?

A

Leptin is made in fat cells and circulates in the bloodstream to suppress hunger and is essentail for controlling long term food intake.

63
Q

What does leptin do?

A

Tells you to stop eating

64
Q

What is the relationship between db mice and leptin?

A

Db mice dont have the receptor, but they overproduce the actual hormone.

65
Q

What is the relationship between ob mice and leptin.

A

They cannot produce the hormone leptin.

66
Q

What are releasing hormones?

A

Hormones whose main purpose is to release other hormones

67
Q

What are tropic hromones?

A

Hormones that have other endocrine glands at their target

68
Q

What is the hypothalamus

A

The portion of the brain that maintains the body’s internal balance (homeostasis) and is the link between the endocrine and nervous system

69
Q

How do pituitary tumors cause phenotypes in growth and physiology?

A

It controls other hormone glads in the body, and secretes many hormones essential for our well being by regulating metabolism, growth, etc. The tumors that change behavior of these hormones can change phenotypes in growth and physiology.

70
Q

What is homeostasis?

A

Maintaining stability in the internal environment

71
Q

How is glucose balanced?

A

Glucagon rises, insulin lowers

72
Q

How is water balanced?

A

Antidiuretic hormone or vasopressin (ADH) rises, and atrial natriuretic hormone (ANH) lowers

73
Q

How is calcium balanced?

A

Parathyroid rises, and calcitonin lowers

74
Q

How is K/Na balanced?

A

ANH rises, while mineralocorticoids lowers

75
Q

What is endocrine signaling?

A

When hormones are secreted into the bloodstream; only target cells with appropriate receptors

76
Q

What is autocrine signaling?

A

When hormones act on the same cells that secreted them

77
Q

What is paracrine signaling?

A

Secreted by one cell and acts on adjacent cells

78
Q

What are the two broad classes of hormones?

A

Liquid-soluble/nonpolar, or water-soluble/polar

79
Q

What are the two ways that hormones can trigger cellular response?

A

Directly, by binding to intracellular receptors and modulating gene transcription, or indirectly binding by binding to cell surface receptors and stimulating signaling pathways

80
Q

What are receptors for lipid-soluble steroid hormones?

A

Cytoplasmic transcription factors (they enter the nucleus upon hormone binding)

81
Q

How are hormones chemical messengers?

A

They affect development, growth, metabolism, sexual function, reproduction & mood

82
Q

In terms of hormones, what causes the final hormonal response?

A

Altered gene expression, altered membrane permeability, altered enzyme activity

83
Q

What two hormones regulate plant growth?

A

Auxin and cytokinin

84
Q

How do auxin and cytokinin regulate plant growth?

A

Plants lack specialized organs for hormone secretion, but theres spacial distribution of hormone production (Auxin to cytokinin ratio determines root versus shoot growth).

85
Q

What is apical dominance

A

The inhibition of axillary buds by apical buds.

86
Q

How does auxin-cytokinin ratio affect devo?

A

Altering auxin-cytokinin ratio can induce different types of development.

87
Q

Which ratios of auxin to cytokinin cause which types of induction?

A

High: root induction
intermediate: callus induction
low: shoot induction

88
Q

What does auxin do at the cellular level?

A

By de-repressing transcription

BIOL 103 (6 decks)

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