Chapter 9 Flashcards

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1
Q

What do the offspring of asexual reproduction receive?

A

All offspring inherit the same number and kinds of genes of its parents.

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2
Q

What are Genes?

A

Sequences of DNA that encode heritable information about traits.

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3
Q

What is a Clone?

A

A genetically identical copy of the parent, barring mutations all offspring of asexual reproduction are clones.

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4
Q

What is an Allele?

A

Each unique molecular form of the same gene.

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5
Q

What are Gametes?

A

The mature reproductive cells formed by the meiosis of germ cells.

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6
Q

What is a Zygote?

A

The first cell of a new individual.

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7
Q

What does it mean if a cell has a diploid number?

A

It means that it has a pair of each type of chromosome.

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8
Q

What are Homologous Chromosomes?

A

A pair of chromosomes that have the same length, shape, and assortment of genes. They appear zipped together during meiosis.

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9
Q

True or False: In Meiosis, the cells go through two cell cycles.

A

True, though it only goes through interphase.

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10
Q

What happens in Prophase 1?

A

Chromosomes were duplicated earlier, in interphase. Now they start to condense. Each pairs with its homologue and swapssegments with it. New microtubules are forming a bipolar spindle. One of the two centrosomes moves to the opposite side of the nuclear envelope, which begins to break up.

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11
Q

What happens in Metaphase 1?

A

Prior to metaphase I, one set of microtubules had tethered one chromosome of each type to one spindle pole and another set tethered its homologue to the other spindle pole. A tug-of war between the two sets has now aligned the chromosomes midway between the two spindle poles.

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12
Q

What happens in Anaphase 1?

A

One of each duplicated chromosome, maternal or paternal, moves to a spindle pole; its homologue moves to the opposite pole. Motor proteins that interact with microtubules bring about the movement.

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13
Q

What happens in Telophase 1?

A

One of each type of chromosome has arrived at a spindle pole. In most species, the cytoplasm divides at this time. All of the chromosomes are still duplicated.

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14
Q

What happens in Prophase 2?

A

In each cell, one of two centrioles moves to the opposite side of the cell, and a new bipolar spindle forms. Some spindle microtubules harness one chromatid of each chromosome to a spindle pole; other microtubules harness its sister chromatid to the other pole.

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15
Q

What happens in Metaphase 2?

A

By now, microtubules from both spindle poles have finished a tug-of-war. They have aligned all of the still-duplicated chromosomes midwaybetween the poles.

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16
Q

What happens in Anaphase 2?

A

The sister chromatids of each chromosome move apart and are now individual, unduplicated chromosomes. Microtubules pull them toward opposite spindle poles as other microtubules push the poles apart. A parcel of one of each type of chromosome will end up near each pole.

17
Q

What happens in Telophase 2?

A

A new nuclear envelope encloses each parcel of chromosomes, so there are now four nuclei. The cytoplasm divides. Each of the daughter cells now has a haploid number (n) of unduplicated chromosomes.

18
Q

What does ‘Crossing Over’ mean?

A

A process by which a chromosome and its homologous partner exchange corresponding segments.

19
Q

True or False: Crossing over between a pair of homologous chromosomesputs novel combinations of alleles in both, which results innovel variations in forms of traits among offspring.

A

True. Gene swapping would be pointless if each type of gene never varied.

20
Q

How many possibilities of combinations are there between human sperm and eggs for maternal and paternal chromosomes?

A

8,388,608 (2^23) combinations.

21
Q

What is a Sporophyte?

A

A diploid multicelled body found in most plant life cycles. Spores form in part of it.

22
Q

What is Gametophyte?

A

A multicelled haploid body inside which one or more gametes form.

23
Q

True or False: In animals, haploid germ cells give rise to gametes.

A

False, in animals diploid cells give rise to gametes.

24
Q

What is Fertilization (in relation to sexual reproduction)?

A

The fusion of the haploid nuclei of two gametes.

25
Q

Why does meiosis precede fertilization?

A

Because if it did not then the chromosome number would double every generation, which would change the individual’s hereditary information.

26
Q

Sexual or Asexual Reproduction: Meiosis, gamete formation, and fertilization.

A

Sexual reproduction.

27
Q

Why do meiosis and fertilization shuffle parental alleles?

A

So offspring inherit new combinations of alleles.

28
Q

Does meiosis half the parental chromosome number?

A

Yes, then the fusion of two gamete nuclei during fertilization restore the parental chromosome number in the zygote.

29
Q

What three events give rise to novel combinations of alleles?

A
  1. Crossing over to prophase 12. The random alignment of maternal and paternal chromosomes at metaphase 13. The chance meeting of gametes at fertilization