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Biology > Topic 3 - Voice of the genome > Flashcards

Topic 3 - Voice of the genome Flashcards

1
Q

Describe the transport of a protein through a cell

A
  1. mRNA is transcribed off DNA and leaves the nucleus
  2. Protein enters RER and assumes 3D shape as it moves through
  3. Vesicles are pinched off the RER contain protein, they fuse to form flattened sacs of the Golgi apparatus
  4. proteins are modified within the Golgi, vesicles are pinched off containing the modified protein
  5. Vesicle fuses with the cell surface membrane releasing its contents (exocytosis)
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2
Q

Sperm cell

A

Sperm cell is motile, it has a flagellum enabling it to swim to egg.

Sperm body contains multiple mitochondria which provide energy through respiration to power the flagellum.

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3
Q

Egg cell (ovum)

A

Large cell incapable of independent movement.

Moved along oviduct from ovary to uterus by ciliated cells and muscle contractions.

Contains lipid drops and proteins to sustain egg till it fuses to uterus wall.

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4
Q

Acrosome reaction

A
  • Acrosome in the head of the sperm nucleus fuses with the sperm cell surface membrane
  • Contains digestive enzymes to digest the zona pellucida
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5
Q

Cortical reaction

A
  • Once sperm penetrates membrane surrounding egg chemicals are released causing the zona pellucida to harden - preventing further sperm entering
  • Sperm nucleus enters egg and fuses with ovum nucleus forming a zygote
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6
Q

Human chromosomes and gametes

A

Humans have 46 chromosome:

  • 22 homologous pairs
  • 1 sex chromosome pair ( XX or XY)

Gametes contain one chromosome from each homologous pair, so when they fuse the zygote has the full 46 chromosomes

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7
Q

Where + why

does meiosis occur

A
  • Occurs in testes/ovaries of animals
  • Helps maintain diploid nature of cells after fertilisation
  • Allows genetic variation to occur among offspring
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8
Q

Independent assoirtment

A

only one chromosome from each pair ends up in a gamete
either chromosome from each pair can end up in any gamete
when joined with other gamete at fertilisation, the individual is guaranteed to be genetically diversity

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9
Q

crossing-over

A

during first meiotic division homologous chromosomes come together as pairs, all 4 chromatids are in contact

at contact point, chromatids break and rejoin - exchanging DNA between non-sister chromatids

several chiasmas (point at which chromatids break) can occur on the length of each pair of chromosomes - giving rise to a large amount of variation

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10
Q

Linkage

A

Any two genes with a locus on the same chromosome are linked together and tend to be passed on as a pair to the same gamete.

Strongly linked genes (close together on same chromosome) makes crossing-over unlikely, they will be inherited as a pair.

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11
Q

sex linkage

A

all the genes on the sex chromosomes are passed on with those that determine sex, they are sex-linked genes.

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12
Q

Male infertility

A

Chemical oscillin is required in sperm cytoplasm for fertilisation to occur.

Controls movement of calcium ions into/out of ovum cytoplasm stores

Low levels of oscillin may be linked to male infertility

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13
Q

Interphase

A

time of intense + organised activity where the cell synthesises new cell components eg organelles, membranes and DNA

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14
Q

G1 phase

A

period between the end of mitosis and start of S phase, period of growth and protein synthesis

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15
Q

S phase

A

period between G1 and G2 phase, DNA synthesis occurs during this period.

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16
Q

G2 phase

A

end of S phase and start of mitosis, period of growth and protein synthesis

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17
Q

Chromatin

A

substance within chromosomes consisting of DNA and protein

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18
Q

Prophase

A

chromosomes condense becoming thicker + shorter, with each chromosome visible as two chromatids

spindle fibres form, nuclear envelope breaks down forming vesicles in cytoplasm

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19
Q

metaphase

A

chromosomes move to centre of cell, centromeres attach to spindle

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20
Q

anaphase

A

spindle fibres shorten, pulling chromatids towards polls of the cell

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21
Q

telophase

A

opposite to prophase, chromosomes unravel and nuclear envelope forms

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22
Q

Cytoplasmic division

A

final reorganisation into two new cells, filaments and microtubules are involved. In plant cell synthesis a plate forms between two new cells.

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23
Q

importance of mitosis

A

Ensures genetic diversity, daughter cells are identical to each other and parent cell

essential for growth and repair
essential for asexual reproduction

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24
Q

growth and repair

A

all cells in the organism have the same genetic material

organism can regenerate and repair damaged parts of their body

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25
Q

asexual reproduction

A

many organisms reproduce without gametes.

They grow copies of themselves by mitosis producing offspring genetically identical to each other + parent

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26
Q

cells in the early embryo

A

After human zygote has undergone 3 complete cell cycles it consists of 8 totipotent cells that can develop into a complete human being

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27
Q

Plant tissue culture

A

Small pieces of plants (explants) are steralised and put on solid agar medium with nutrients + growth regulators

Cells divide and form callus (mass of undifferentiated cells)

Altering growth regulators in medium enables callus to differentiate forming groups of cells similar to plant embryo

Embryo develops into plant genetically identical to original plant

28
Q

totipotent cells

A

undifferentiated stem cells which have the ability to differentiate and give rise to all specialised cells. They can give rise to more totipotent cells and to a whole human being

29
Q

pluripotent cells

A

undifferentiated cells that also have the ability to differentiate, but as they are inactive they cannot differentiate into all cell types like totipotent stem cells.

30
Q

multipotent cells

A

Can develop into more than one cell type, but are more limited than pluripotent

31
Q

unipotent cells

A

can only mature into one type of cell

32
Q

Therapeutic cloning

A

Diploid cell is removed from patient

Its cell or nucleus is fused with ovum without its haploid nucleus – diploid cell similar to zygote is formed

Cells could be stimulated to divide by mitosis

After 5 days blastocyst forms stem cells which are then isolated, and can be developed into tissue

This produces cell lines, which are genetically identical to patient from which diploid cell was taken

33
Q

adult stem cell use

A
  • Used in bone marrow transplants
  • Treat burn patients
  • Blood vessel production
34
Q

Takahashi and Yamanaka 2006

A

reported successful reprograming of somatic mouse cells to make them pluripotent

They are known as induced pluripotent stem cells.

Human IPSC have since been produced resembling human embryonic stem cells

35
Q

under what circumstances in embryonic cell research legally allowed

A

Promote advances in treatments for infertility

Increase knowledge about causes for miscarriage

Develop more effective methods for contraception

36
Q

what controls development of a cell

A

nucleus and chemical messengers travelling through cytoplasm

37
Q

dolly the sheep’s cloning process

A

They transported a nucleus from a mammary gland cell of one sheep into another sheep’s enucleated egg cell

The cell was then stimulated by electric shocks so it divides by mitosis

The diploid cell that formed the embryo was implanted into another adult sheep

The surrogate mother gave birth to a lamb who was chromosomally identical to mammary cell donor

38
Q

what did dolly prove

A

The successful birth of Dolly suggests the cell must have contained all the info for making a complete organism

39
Q

problems with cloning

A

Process not safe to try on humans
Animals cloned have health problems
Dolly got arthritis at a young age
Many factors could lead to low success rate

40
Q

David and Sargent and gene expression

A

They extracted mRNA from undifferentiated and differentiated frog cells

Complimentary DNA strands were produced for all mRNA in differentiated (gastrula) cells using reverse transcriptase

These cDNA strands were mixed with (blastula) mRNA from undifferentiated cell

Complimentary strands of cDNA mRNA combined to produce double strand hybrids

When these hybrid strands were separated out, there remained a range of cDNA strands that had not been hybridised

The cells were expressing some of the same genes but also some different ones.

41
Q

what is the epigenome

A

Epigenome influences what genes can be transcribed in a cell. DNA is wrapped around histone proteins, both DNA and histones have chemical markers attached to their surface. These chemical markers make up the epigenome

42
Q

what happens when DNA is wrapped tightly around histone

A

genes are inactive, they can’t be transcribed. Gene therefor cannot make protein = it is switched off.

43
Q

eukaryotes gene expression

A

Genes in uncoiled, accessible regions of the eukaryotic DNA can be transcribed into mRNA.

Enzyme RNA polymerase binds to section of DNA adjacent to gene to be transcribed (promoter region).

44
Q

when is transcription prevented in eukaryotes

A

Transcription of gene can be prevented by protein repressor molecules attaching to the DNA of the promoter region – blocking attachment region.

Also, repressor protein can attach to regulator protein preventing it from attachment.

In both cases the gene is switched off and cannot be transcribed within cell.

45
Q

what caused FOP

A

Inherited condition caused by gene mutation:

Bone cells are normally produced in growing limbs and in process where skeleton develops.

Here genes are expressed that produce all proteins needed to become specialised bone cells.

46
Q

How are cells organised into tissue

A

Cells have specific recognition proteins (adhesion molecules) on their cell surface membrane.

Adhesion molecules helps cells recognise others like themselves + stick to them.

Small part of recognition protein is embedded in cell surface membrane, longer part extends from the membrane.

The extended part binds to complimentary proteins on adjacent cells.

47
Q

cell

A

In multicellular organisms, cells are specialised for particular functions

48
Q

tissue

A

group of cells working together to carry out one function

49
Q

organ

A

group of tissues working together to carry out one function

50
Q

organ system

A

group of organs working together to carry out a function

51
Q

Gene expression and develop

A

Sequence of transcription and translation of genes determines sequence of changes during development.

Epigenome helps control changes from single-celled zygote to fully formed adult.

During development epigenetic changes bring about specialisation of cells.

Signals from inside and outside the cell result in changes to the epigenome that affect genes transcribed.

Copying of epigenome during DNA replication ensures that changes occurring during development are passed on to new cells.

52
Q

Name 4 organ types in hermaphrodite flowers

A

petals
sepals
male stamens
female carpels

53
Q

discontinuous variation

A

Not affected by the environment, controlled by genes at a single locus.

54
Q

continuous variation

A

characteristics affected by both genotype and the environment

55
Q

monohybrid inheritance

A

each locus is responsible for a different heritance feature, eg one gene codes for eye colour and another codes for height

56
Q

polygenic inheritance

A

many genes involved in the expression of a characteristic

57
Q

multifactorial inheritance

A

conditions where several genetic factors and one or more environmental factors are involved

58
Q

Melanin production

A

Melanin is made in melanocytes (special cells) found in skin + hair follicles.

These are activated by melanin stimulating hormone (MSH). There are receptors for MSH on melanocyte cells.

Melanocytes place melanin into organelles called melanosomes.

Melanosomes are transferred to nearby skin + hair cells where they collect around the nucleus, protecting DNA from harmful UV.
More receptors -> darker hair + skin -> more protection from sunburn.

59
Q

behaviour and the epigenome, rat experiment

A

Epigenetic difference between rats as pups grew up to be like their mother.

Offspring of good mothers (licked + groomed a lot) and bad mothers (rarely groomed + licked) were swapped.

Found two sets up pups were epigenetically different.

GR gene in pups with bad parent switched off due to methylation of gene.

Gene produces receptor protein that binds to stress hormone causing calm signals to be sent.

Low levels of GR protein = hormone level remains higher in blood and pup feels more stress.

60
Q

Define cancer

A

when rate of cell division exceeds rate of cell death

61
Q

Oncogenes (cancer triggers)

A

Code for proteins that stimulate transition from one stage to another in cell cycle.

DNA mutations or epigenetic changes in these genes can lead to cell cycle being continually active -> excessive cell division = tumour.

62
Q

tumour suppressor gene (cancer triggers)

A

Produces suppressor proteins that stop the cycle.

DNA mutations or epigenetic changes in these genes eg more methylation inactivity means there’s no brake in the cycle.

63
Q

Smoking - chemical risk factor for cancer

A

Greatest chemical risk is smoking which increases risk of lung cancer.

Tar lodges in bronchi and damages DNA surrounding epithelial cells.

64
Q

UV light - physical risk factor for cancer

A

UV light physically damages DNA in skin cells.

Mole affected by UV can develop into tumour, if not removed can spread around the body.

65
Q

Radicals and cancer

A

Radicals come from diet, the environment and can be produced by DNA’s own metabolism.

Radicals contribute to aging and cancer due to damage to DNA.

Biology (6 decks)

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