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Mol / Cel Biology > Lecture 2 > Flashcards

Lecture 2 Flashcards

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1
Q

What is the purpose of the nucleus?

A

Controlling center of the cell.

Contains linear DNA molecules

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2
Q

What is the function of nuclear envelope?

A

Double layered membrane complex.
Separates the nucleus from cytoplasm.
Separates ‘‘copy’’ of information (mRNA synthesis) from protein synthesis

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3
Q

Outer nuclear membrane consists of?

A

It’s linked with rough ER

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4
Q

Inner nuclear membrane consists of?

A

Contains specific set of integral membrane proteins that establish connections to chromatin and with nuclear lamina

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5
Q

What is the function of nuclear pore?

A

Protected exchange of components between the nucleus and cytoplasm

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6
Q

What can you tell about the linkers of nucleoskeleton and cytoskeleton (LINC complex?)

A

It positions the nucleus.
It coordinates nuclear and cytoplasmic activities.
Involved in mechanical force transmission from cytoskeleton to the nucleus

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7
Q

What is nuclear lamina?

A

Structure attached to the inner membrane and chromatin

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8
Q

What does nuclear lamina consists of?

A

Proteins called nuclear lamins.
A-type, B-type and C-type lamins

A and C are isoforms, coded by one gene

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9
Q

What is the function of nuclear lamina?

A

Lamina binds to the integral proteins of inner membrane.

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10
Q

What are laminopathies?

A

Changes in the sequence of lamins and lamina integrating proteins, that codes DNA regions -> leads to group of inherited disorders

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11
Q

What is nucleoplasm?

A

A jelly like fluid inside the nucleus, it’s major components are nucleoproteins

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12
Q

What are histones?

A

They are high MW proteins that contains basic amino acids, and have a positive charge.

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13
Q

How many classes of histones there are?

A

Total of five

H1, H2s, H2B, H3, H4

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14
Q

What is the main function of histone?

A

It contributes to the packing of DNA -> DNA is wrapped around histone octamer complex

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15
Q

How does the Histone-DNA-wrapping happens?

A

Postively charged amino acids of histones will form ionic bounds with negatively charged DNA

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16
Q

What are non-histone proteins?

A

Small, acidic proteins or enzymes (DNA or RNA polymeraze etc.)

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17
Q

Majority of the DNA is packed into? (in eukaryotic cell)

A

Nucleosomes (Histones+DNA)

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18
Q

What are nucleosomes made of?

A

Eight histone molecules (octamer)

H2A, H2B, H3, H4

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19
Q

Linker DNA?

A

DNA that links nucleosomes one to the next

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20
Q

With what linker DNA tightly bounds with?

A

Histone H1 ->This complex closes nucleosome and form chromatosome

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21
Q

What happens in Interphase?

A

Cell is actively expressing its genes and synthesizing proteins, DNA is replicated and chromosomes are duplicated.

22
Q

Ones DNA replication is complete, what phase can be unlocked?

A

M phase.

23
Q

What happens in M phase when mitosis occurs and the nucleus is divided into two daughter nuclei?

A

The chromosomes condense, the nuclear envelope breaks down and the mitotic spindle forms

24
Q

What happens when mitotic chromosomes are captured by the mitotic spindle?

A

One complete set of chromosomes is pulled to each end of the cell, nuclear envelope re-forms around each chromosome set

25
Q

What happens in the final M phase?

A

The cell divides to produce two daughter cells

26
Q

What can you tell about euchromatins?

A

They have a high level of gene expression and they are early replicative, less condence

27
Q

What can you tell about heterochromatins first of all?

A

Limited / no gene expression, associated with telomere and centromere.
Late replicative.
Only in eukaryotic cells.

28
Q

What is a constitutive heterochromatin?

A

Contains highly repetitive sequences of genetically inactive DNA.
Serves as structural element of the chromosome
It is stable during all stages of development in all tissues.

29
Q

What is a facultative heterochromatin?

A

It makes up the inactive X chromosome in female somatic cells (Barr body).
It is characterized by presence of LINE-type repeated sequences.
It’s reversible.

30
Q

What are constitutive- and facultative heterochromatin methylated on?

A

Constitutive is mythylated on cytosine.

Facultative is methylated on CpG islands (gene control regions).

31
Q

Functions of heterochromatin?

A

Centromere function.
Organisation of nuclear domains.
Gene repression.

32
Q

What is a chromosome?

A

The tight coiling of the 250 nm fibre produces the chromatid of chromosome.

33
Q

What happens to chromosome in the S phase? (interphase)

A

Replication of DNA takes place and two identical chromatids are produced.

34
Q

What phase chromosomes can be observed during cell devision?

A

Metaphase chromosomes

35
Q

What can you say about metaphase chromosomes?

A

Cohesin attaches to the chromosome during replication and ensures sister chromatic contact during cell division.

36
Q

Sister chromatids?

A

Two copies of one chromosome.

37
Q

What are telomeres?

A

Repeated nucleotide sequences which are species specific.
TTAGGG repeats in humans.
3’ strand ended is single stranded, forms a cap.

38
Q

Telomeres functions?

A

Counts how many times cell can divide; maintaining normal genome.

39
Q

Uncapped telomeres are able to?

A

Activate the DNA damage response and cause end-to-end fusions, resulting in chromosomal instability

40
Q

Karyotype: somatic cells have how many chromosomes?

A

Diploid set of chromosomes (2n) - 46

41
Q

Karyotype: germ cells have how many chromosomes?

A

Haploid set of chromosomes (1n) - 23

42
Q

Sex-chromosome?

A

Determines the sex and sex-linked features.

Humans have two sex chromosomes: X and Y

43
Q

Each individual cell contains two sex chromosomes which are?

A

In diploid cell Female-XX and Male -XY

44
Q

Difference between the activation of X chromosome in male and female?

A

In females, one X chromosome is inactivated (Barr body) in all somatic cells.

In males, X chromosome is active (no barr body)

45
Q

How many barr bodies in female: 47, XXX?

A

Two, because female needs one active, would not lead to any specific diseases.

46
Q

What is the function of a nucleolus?

A

The site of a ribosomal (rRNA) transcription, ribosomal assembly

47
Q

What can you say about prokaryotic chromosome?

A

Nucleoid consists of DNA and RNA molecules with nucleoproteins, membrane free.

DNA is circular, not attached with histones.

One information of genetic copy - haploid organism.

48
Q

What can you say about prokaryotic chromosomes plasmids?

A

Contains small part of genetic information which contributes to the sensitivity to various toxic substances (antibiotics etc.)

Plays a role in genetic recombination

49
Q

Mitochondrial chromosome?

A

Self-replicating organelle.

It’s matrix has a complex mixture of proteins and enzymes.

Important for synthesis of ATP molecules, mitochondrial ribosomes, tRNA’s and mitochondrial DNA

50
Q

What is mitochondrial DNA? (mtDNA)

A

Circular, negatively supercoiled.
Contains 4-5 mtDNA copies.
Toposiomerases: Top1mt, Top3alpha, Top2beta

51
Q

Features and functions of the mitochondria?

A

Self-replication.
Aerobic ATP production.
Ion homeostasis.

Mol / Cel Biology (17 decks)

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