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Biology 1 Exam 3 > New Exam 3 > Flashcards

New Exam 3 Flashcards

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1
Q

How do spindles move the chromosomes?

A

In the Prometaphase, Nuclear
envelope breaks down.
Spindle fibers contact
chromosomes at kinetochore.

Spindles shorten because
tubulin subunits of the
microtubules are lost from
their plus ends at the
kinetochore.

As the microtubule shortens
and the detach-move-reattach
cycle of the motor proteins
repeats, the chromosome is
pulled to one end of the
mitotic spindle

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2
Q

How do spindle microtubules attach to chromosomes? What is kinetochore?

A

Spindle microtubules attach to the chromosome by using the kinetochores to attach to the centromere where during Anaphase
______________________________
Kinetochore microtubules from each mitotic spindle attach to one of the sister chromatids of each chromosome
Attachment occurs in the centromere region at the kinetochore

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3
Q

How is metaphase characterized?

A

Alignment of chromosomes along the cell’s equator.

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4
Q

Which cytoskeletal proteins are involved in cleavage furrows in animal cell cytokinesis?

A

Actin–myosin (and their interactions)

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5
Q

What is MPF? What are the components of MPF, and how do they function?

A

Mitosis promoting factor (MPF), that induces M phase in interphase
cells. MPF contains 1 protein kinase and 1 cyclin. The protein kinase is a
phosphorylation enzyme that
catalyzes the transfer of a
phosphate group from ATP to
a target protein. The cyclin subunit functions as a regulatory protein

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6
Q

What happens to cyclin-dependent kinase during mitosis?

A

The MPF protein kinase is a cyclin-dependent kinase. Thus, it is active
only when bound to the cyclin subunit, and it is also known as Cdk.

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7
Q

What are the phases of cell cycle?

A

G1,(S)ynthesis, G2, (M)itosis phase
Interphase also includes two
gap phases, during which no
DNA synthesis occurs, and the S phase. G1 phase - the first gap and occurs before the S phase. G2 phase - the second gap and occurs between S phase
and mitosis. During the gap phases, cell
grows larger, additional
cytoplasm is made, and
organelles replicate in
preparation for cell division.

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8
Q

What are the checkpoints of cell cycle?

A

G1: Passes checkpoint if:
* cell size is adequate
* nutrients are sufficient
* social signals are present
* DNA is undamaged

Goes into S phase if passes, if fails goes into G0

G2: Pass checkpoints if:
* chromosomes have
replicated successfully
* DNA is undamaged
* activated MPF
is present

Stops growing if it fails

M phase: (in metaphase)
1. chromosomes have
attached to spindle
apparatus
2. chromosomes have
properly segregated
and MPF is absent

Cell growth ceases if chromosomes dont attach to mitotic spindle properly

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9
Q

What are tumor suppressors?

A

p53 is an example of a tumor suppressor; intitates apoptosis and makes sure destorys damaged cells. Damage to the p53 gene can
lead to uncontrolled cell division

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10
Q

During which stage of interphase do centrioles duplicate?

A

S phase

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11
Q

During which phase of mitosis do chromosomes condense?

A

Prophase

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12
Q

During which phase of mitosis do nuclear envelopes form?

A

Telophase

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13
Q

During which phase of cell cycle DNA replication occurs?

A

S phase

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14
Q

For meiotic cells, when does DNA replication occurs?

A

S-phase of the Interphase before Meiosis I begins

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15
Q

At which phase of mitosis do the sister chromatids become daughter chromosomes?

A

Anaphase

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16
Q

What is the difference in chromosome number between diploid and haploid cells?

A

diploids are 2*haploids. Diploid cells contain two complete sets. Haploid organisms, on the other hand, only contain one complete chromosome set

17
Q

What is chromosome synapsis? When does crossover between homologous
chromosomes take place?

A

Chromosome synapsis is the pairing of two chromosomes that occurs during meiosis. It allows matching-up of homologous pairs prior to their segregation, and possible chromosomal crossover between them. The crossing over of homologous chromosomes occurs in late prophase I of meiosis.

18
Q

When do homologous chromosomes undergo recombination?

A

prophase I

19
Q

What is nondisjunction?

A

If both homologs or both sister chromatids move to the same pole of the parent cell. Lead to trisomy (Down’s with chromosome 21) or monosomy.

20
Q

What are gene alleles?

A

An allele is one of two or more versions of DNA sequence (a single base or a segment of bases) at a given genomic location.

21
Q

What was the most significant conclusion that Gregor Mendel drew from his experiments with pea plants?

A

Traits are inherited in discrete units. One from each parent.

22
Q

What is independent segregation? What is independent assortment?

A

Principles of segregation, which has become known as Mendel’s First Law: the first of Mendel’s laws states that genes are transferred as separate and distinct units from one generation to the next.

Principles of independent assortment, also known as Mendel’s Second Law: the law of independent assortment, is that the alleles of a gene pair located on one pair of chromosomes are inherited independently of the alleles of a gene pair located on another chromosome pair and that the sex cells containing various assortments of these genes fuse at random with the sex cells produced by the other parent

23
Q

When does independent assortment of chromosomes occurs?

A

meiosis 1 (prophase1?)

24
Q

How do gametes form?

A

Gametes are formed through meiosis (reduction division)

25
Q

How do identical twins form?

A

when a single egg (zygote) is fertilized. The egg then divides in 2, creating identical twins who share the same genes.

26
Q

What is telomere? What is the function of telomerase?

A

Telomere is the region at the end of a linear chromosome and consists of short, repeating stretches of bases, and does
not contain genes.

During DNA synthesis, No primer for DNA
polymerase near the end, so unreplicated end will degrade, shortening chromosome. Telomerase prevents the lagging strand from getting shorter with each replication by adding more
repeating bases to the end of the
lagging strand, catalyzing the
synthesis of DNA from an RNA
template carried with it.

27
Q

How is telomerase activity implicated in senescence and cancer in somatic cells?

A

In a normal somatic cell at some point, the telomeres become critically short,
and this attrition leads to cell senescence, where the cell is unable to divide, or
leads to apoptotic cell death. With telomerase, the cell can continue to divide indefinitely as it gets to keep the telomeres.

28
Q

What is karyotyping?

A

a test to examine chromosomes in a sample of cells. This test can help identify genetic problems as the cause of a disorder or disease.

29
Q

What is directionality on a DNA strand?

A

5 prime carbon to 3 prime carbon (5’ → 3’)

30
Q

What is complementary base pairing in DNA?

A

A base pair consists of two complementary DNA nucleotide bases that pair together. One Purine (A,G)and one pyrimidine(T, C). (AT and GC)

31
Q

How are the two strands of DNA double helix held together?

A

Two DNA strands line up
in the opposite direction to
each other - antiparallel
fashion. The secondary structure is
stabilized by
complementary base
pairing through Hydrogen bonds

32
Q

What are the enzymes and their functions involved in DNA replication?

A

Helicase - break hydrogen bonds between complementary base pairs during DNA replication

Topoisomerase - removes supercoils that are generated during DNA replication

DNA polymerase - joins DNA fragments during DNA replication

SSBP - Single-strand DNA-binding proteins (SSBPs) stabilize single strands

Ligase - Ligase is an enzyme that catalyzes the binding of two molecules (typically seen with different okazaki fragments)

Primase - synthesizes short RNA sequences called primers, which serve as starting points for DNA synthesis in lagging

Replisome - one large, multi-enzyme machine involving most of the enzymes

33
Q

What is replisome?

A

The enzymes responsible for DNA synthesis around the replication fork are
joined into one large, multi-enzyme machine referred to as replisome

34
Q

Why and how are the two strands of the DNA are replicated differently?

A

During DNA replication, DNA is seperated and there would be a side going from 5’ to 3’ and a side going from 3’ to 5’. For the side going 5’ to 3’, the replication DNA would have to go 3’ to 5’, and replication can only occur from 5’ to 3’, so the DNA starts off at a further end and works backwards (5’ to 3’) making small fragments called Okazaki fragments.

35
Q

What are the Okazaki fragments?

A

Small fragments of DNA working its way through the lagging strand

36
Q

How is the energy required for DNA replication provided?

A

From the phosphate groups. triphosphate nucleotide attached to 3’ (phosphodiester bond) and PPi (2 phosphate) gets released as energy (H2O also gets released).

37
Q

What is a major difference between eukaryotic DNA replication and prokaryotic DNA replication?

A

Prokaryotic chromosomes have a single origin of replication, while eukaryotic chromosomes have multiple origins of replication (lagging strand).

38
Q

What are the three mechanisms of DNA repair system?

A

nucleotide excision repair, base excision repair, and mismatch repair.

39
Q

What is the function of Microtubule Motor Proteins?​

A

Microtubule motor proteins disassemble the spindle microtubule that is connected to the kinetochores of the chromosomes. ​

Biology 1 Exam 3 (2 decks)

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