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Fundamentals of Genetics > Chromosomes and Cell Division > Flashcards

Chromosomes and Cell Division Flashcards

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Biology 101 flashcards
1
Q

Name the stages of the cell cycle.

There are 9.

A
  • Interphase: G1, G0 (nondividing), S phase, G2
  • Prophase
  • Prometaphase
  • Metaphase
  • Anaphase
  • Telophase
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2
Q

What is the chromosome structure during interphase?

A

loosely coiled, replicated chromosomes

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3
Q

What is the chromsome structure during prophase?

A

Chromosomes condense

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4
Q

What is the chromosome structure during prometaphase?

A

Spindle fibers attach to chromosomes and the chromosomes condense

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5
Q

What is the chromosome structure during metaphase?

A

The chromosomes align in the center

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6
Q

What is the chromosome structure during anaphase?

A

Centromeres divide and sister chromatids move to opposite poles

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7
Q

What is the chromosome structure during telophase?

A

Chromosomes decondense, nuclear membrane reforms

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8
Q

What is the chromosome structure during cytokinesis?

A

The cytoplasm divides, and the chromosomes uncoil.

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9
Q

What is the goal of mitosis?

A

production of two cells with the same number of chromosomes as the parent cell

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10
Q

What is the goal of meiosis?

A

production of sex cells that contain 1/2 the number of chromosomes (haploid), with genetic diversity through recombination

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11
Q

Describe the stages within interphase.

A

intensive metabolic activity, cell growth, and cell differentiation are evident
* G1 (gap I): period during interphase where no DNA synthesis occurs. Before S phase
* S Phase: DNA is synthesized before the cell enters mitosis
* G2 (gap II): period during interphase where no DNA synthesis occurs. After S phase
* G0 stage: Cells that enter G0 remain viable and metabolically active but are not proliferative
* During interphase, the nucleus is filled with chromatin fibers that are formed as the chromosomes uncoil and disperse after the previous mitosis
* Once G1, S, and G2 are completed, mitosis is initiated

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12
Q

Briefly describe the stages of mitosis.

A
  • prophase: centrioles migrate to opposite ends of the cell, nuclear envelope begins to break down, chromatin fibers begin to condense, sister chromatids are visible
  • prometaphase: chromosome movement
  • metaphase: chromosomes begin to line up in center of cell, spindle fibers bind to kinetochore (in centromere) to move them
  • anapase: sister chromatids disjoin from each other and are pulled to opposite ends of the cell
  • telophase: cytokinesis occurs, chromosomes uncoil and become diffuse, spindle fibers disappear and nucleolus reforms
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13
Q

What is an allele?

A

alternative forms of the same gene

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14
Q

what is a locus?

A

gene sites along the lengths of chromosomes

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15
Q

what is a metacentric chromosome?

A

the centromere is in the middle of the chromosome

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16
Q

what is a submetacentric chromosome?

A

the centromere is located between the middle and the end of the chromosome

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17
Q

What is an acrocentric chromosome?

A

the centromere is close to the end

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18
Q

What is a telocentric chromosome?

A

the centromere is at the end

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19
Q

What is a karyotype?

A

An individuals complete set of chromosomes. Shows the double structure of two parallel sister chromatids connected by a centromere

20
Q

What is a zygote?

A

a single-celled fertilized egg. most multicellular diploid organisms begin life as zygotes.

21
Q

Briefly describe the stages of meiosis.

A

Prophase I: diploid cell w/ duplicated genetic material. Tetrads are two sister chromatids joined at the centromere. Cross over occurs.
Metaphase I: tetrad interacts with spindle fibers and starts moving to metaphase plate
Anaphase I: one half of the tetrad (dyad) is pulled to each pole
Telophase I: nuclear membrane forms
Prophase II: dyad is composed of one pair of sister chromatids
Metaphase II: centromeres are positions onto the metaphase plate
Anaphase II: sister chromatids of each dyad are pulled to opposite poles
Telophase II: cytokinesis occurs and monads are in each daughter cell (4 total)

22
Q

What is spermatogenesis?

A

Production of male gametes
* occurs in testes
* undifferentiated diploid germ cell, spermatogonium grows to become a primary spermatocyte
* spermatocyte undergoes meiosis I
* secondary spermatocytes undergo meiosis II and produces spermatids
* spermatids go through spermigenesis to become spermatozoa (sperm)

onset: species reproductive cycles. may be continuous/occur periodically

23
Q

What is oogenesis?

A

production of female gametes
* oogonium matures into a primary oocyte
* in meiosis I, primary oocyte divides unequally:
* daughter cells receive equal amounts of the genetic material but all of the cytoplasm goes to the primary oocyte, first polar body is produced
* at puberty (once a month), the oocyte divides through meiosis II and then is arrested as an ootid, second polar body is produced
* differentiates into a ovum

24
Q

what is a heterogametic sex?

A

the sex of a species where an individual’s gametes have non-matching sex chromsomes
e.g. in humans, men have an XY

25
Q

What is homogametic sex?

A

the sex has sex chromosomes that do not differ in morphology. Results in one kind of gamete. Female humans are homogametic because they contain XX chromosomes.

26
Q

What is Klinefelter Syndrome (47, XXY)

A

There is an extra X chromosome
* result of nondisjunction: failure of sex chromosomes to segragate properly
* tall, long arms and legs
* 50% affected produce sperm (low sperm count, most are sterile)
* no cognitive reduction
* occurs in 1/660 male births

27
Q

What is Turner syndrome? (45,X)

A

There is a missing sex chromosome
* result of nondisjunction: failure of sex chromosomes to segregate properly
* female internal and external genitalia
* ovaries are rudimentary
* short stature
* skin flaps on neck
* underdeveloped breasts
* intelligence is normal usually
* occurs in 1/2000 female births

28
Q

What is 47, XXX Syndrome?

A
  • additional X chromosome
  • triplo-X
  • often are completely normal
  • sometimes women have underdeveloped secondary characteristics or intellectual disability
29
Q

What is 47, XYY Condition?

A
  • additional Y chromosome
  • above average in height and more frequently violent
  • subnormal intelligence, personality disorders
  • some may be completely normal
30
Q

What is the Lyon Hypothesis?

A

the inactivation of X chromosomes occurs randomly in somatic cells early in embryonic development
* once inactivation occurs, all descendant cells ahve the same X chromosome inactivated as their progenitor cell

31
Q

What is Down Syndrome or Trisomy 21?

A
  • extra 21st chromosome
  • share similar physical characteristics
32
Q

What is aneuploidy?

A

When an organism gains or loses one or more chromosomes but not a complete set
* monosomy: the loss of a single chromsome from an otherwise diploid genome
* trisomy: the gain of one chromosome in an otherwise diploid genome

33
Q

What is euploidy?

A

When complete haploid sets of chromsomes are present

(this is preferred)

34
Q

What is Polypoidy?

A

When two or more sets of haploid chromosomes are present
* triploid: three sets
* tetraploid: four sets … etc.

35
Q

What is a nondisjunction?

A

When pair homologs fail to disjoin during segregation
* disrupts normal distribition of chromosomes into gametes

36
Q

What causes chromsomal abberations?

A

Nondisjunctions, deletions, translocations, inversions, duplications

37
Q

Why does advanced maternal age increase risk in nondisjunctions resulting in syndromes such as Trisomy 21?

A
  • meiosis is initiated in all eggs of a female when she is a fetus, and then development is arrested
  • when ovulation begins, meiosis is reinitatied in one each during each ovulatory cycle
  • each ovum that is released is a month older than the one before it
  • genetic counselling is recommended for women who get pregnant late in her reproductive years
38
Q

What is Patau Syndrome and Edwards Syndrome?

A
  • the two other human trisomies that survive to term (excluding Down syndrome)
  • Patau: 47, 13+
  • Edwards: 47, 18+
39
Q

What is deletion?

Distinguish between a terminal and intercalary deletion

A

a missing piece of a chromosome when it breaks in one or more places and a portion of it is lost
* terminal: deletion at the end of a chromosome
* intercalary: deletion in the interior of a chromosome

40
Q

What is Cri du Chat Syndrome?

A
  • result of a deletion of a small terminal portion of chromosome 5
  • 46,5p- :meaning all 46 chromosomes are there but some or all of the p arm of one member of chromsome 5 pair is missing
  • characteristic crying sound in infants
  • intellectual and developmental disabilities
41
Q

What is a duplication?

A
  • when any part of the genetic material is present more than once in the genome
  • a repeated segment of a chromosome
  • may be the result of unequal crossing over between synapse chromosomes during meiosis
  • or thorugh a replication error prior to meiosis
42
Q

What is an inversion?

Distinguish between paracentric and pericentric inversions.

A
  • a chromsomal abberaiton in which a segment of a chromsome is turned around 180º within a chromosome
  • rearranges the linear gene sequence
  • requires a break along two points and then reinsertion of inverted segment
  • paracentric: the centromere is not part of the rearranged chromosome segment
  • pericentric: the centromere is part of the inverted segment
43
Q

What is a translocation?

Include the definition of a reciprocal translocation.

A

the movement of a chromsomal segment to a new location in the genome
* reciprocal translocation: exchange of segments between two nonhomologous chromosomes
* genetic information is not lost or gained, there is a rearrangement of material

44
Q

Name the chromosomal abberations where there is NO loss of genetic material

A
  • translocations
  • inversions
45
Q

Name the chromsomal abberation(s) where there IS a loss of genetic material

A
  • deletion
46
Q

Name the chromomal abberation(s) where there is a gain of genetic material

A
  • duplication
47
Q

What is the difference between genotype and phenotype?

A
  • phenotype: physical appearance
  • genotype: genetic consitution

Fundamentals of Genetics (6 decks)

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