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Alevel Bio > T3 Voice of the Genome > Flashcards

T3 Voice of the Genome Flashcards

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Biology 101 flashcards
1
Q

List some common features of cells including their function

A

-DNA - it is membrane-bound in the nucleus in eukaryotic cells and contained in plasmids and circular DNA in prokaryotes
-Cell surface membrane (AKA plasma membrane)
- phospholipid bilayer containing proteins. Forms partially permeable barrier. Controls what enters and leaves cells by exocytosis etc.
-Cytoplasm - site of cell chemical reactions, consists of fluid cytosol, suspends organelles in a structure in a cell.

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2
Q

structure and function of eukaryotic mitochondrion?

A

-Provides ATP as energy after aerobic respiration
-Inner membrane folded into the liquid matrix to form cristae (finger-like projections)
-Inner membrane and outer membrane
-Contains 70s ribosomes

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3
Q

structure and function of eukaryotic nucleolus?

A

-dense body within nucleus
-synthesis of ribosomes

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4
Q

structure and function of eukaryotic centrioles?

A

-made of small, hollow, protein cylinders called microtubules
-provide spindles for cellular division
-not usually found in plants cells but is in all animal cells

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5
Q

structure and function of eukaryotic smooth ER?

A

-no attached ribosomes
-production of lipids and hormonal steroids for reproduction
-synthesis and processing of these molecules

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6
Q

structure and function of eukaryotic rough ER?

A

-folds and processes proteins made on ribosomes attached during translation
-transports proteins to other parts of cells using transport vesicles
-flattened sacs
-membrane bound
-fluid filled
-ribosomes attached to outer surface

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7
Q

structure and function of Golgi apparatus/body?

A

-processes and packages new lipids and proteins
-modifies proteins from transport vesicles (e.g. adding carbohydrates to proteins forming glycoproteins)
-makes digestive enzymes in lysosomes
-packages protein into secretory vesicles

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8
Q

structure and function of eukaryotic lysosome?

A

-breakdown of unwanted structures in cell
-destruction of whole cell upon replacement
-contains digestive enzymes at are kept separate from cytoplasm
-destroys invading cells/pathogens
-round organelle
-membrane-bound
-no clear internal structure

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9
Q

structure and function of eukaryotic nucleus?

A

-contains chromosomes containing genetic material
-contains genes controlling protein synthesis
-contains pores which allow transport between cytoplasm and nucleus
-controls DNA transcription
-surrounded by double membrane
-surrounded by nuclear envelope
-contains chromatin that are made of DNA and proteins
-contains nucleolus

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10
Q

structure and function of eukaryotic ribosomes

A

-site of translation in protein synthesis
-very small organelle (70S in eukaryotic cells)

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11
Q

Explain role of rough ER and Golgi apparatus in transporting proteins around a cell

A

-DNA is transcribed in nucleus
-mRNA leaves the nucleus through a nuclear pore
-protein made on the ribosome of the rough ER enter the rough ER
-protein moves through the rough ER, assuming a 3D shape
-transport vesicles containing protein pinch off the rough ER and travel to Golgi body
-transport vesicles fuse with Golgi A. to form flattened sacs
-proteins are modified within Golgi A.
-secretory vesicles pinch of the Golgi A. and contain modified protein
-vesicle fuses with cell surface membrane and release protein by exocytosis

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12
Q

structure and function of prokaryote mesosome

A

-infolding of the plasma membrane
-site of respiration

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13
Q

structure and function of prokaryote plasmid

A

-contains genes for antibiotic resistance
-not in eukaryotes
-circular shape with no loose ends

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14
Q

structure and function of prokaryote cell wall

A

-made up of peptidoglycan (polypeptide and polysaccharide)
-maintains structure
-prevents cell bursting after osmosis

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15
Q

structure and function of prokaryote ribosomes

A

-smaller than eukaryotic ribosomes (eukaryotic = 80s, pro =70s)
-carry out translation

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16
Q

structure and function of prokaryote slime capsule

A

-protection from phagocytes
-slimy layer
-prevents dehydration

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17
Q

structure and function of prokaryote flagellum

A

-motion
-different structure to eukaryotic flagellum
-hollow and cylindrical
-thread like
-rotates

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18
Q

structure and function of prokaryote pili

A

-fine protein strands
-helps with adhesion to various surfaces
-DNA transferred between bacteria through pili

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19
Q

structure and function of prokaryote cytoplasm

A

-suspends organelles within
-chemical reaction occur within

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20
Q

structure and function of prokaryote circular DNA

A

-suspended in cytoplasm
-not bound to histone proteins
-contains genetic material

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21
Q

describe the adaptation of a sperm cell

A

-acrosome - contains acrosin and digestive enzymes to break down ovum zona pellucida
-streamlined - increases speed and decreases resistance when getting to ovum
-mitochondrion arranged in spiral in middle - provide ATP for energy for sperm tail motion
-flagellum - moves in whip-like motion, allows sperm to be mobile and swim towards ovum
-haploid nucleus - contains complementary haploid genetic material for zygote

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22
Q

describe adaptations of an egg cell

A

-cytoplasm - contains proteins and lipid food reserves for developing embryo
-cortical granules - release enzymes to thicken jelly-like layer
-haploid nucleus - contains half the genetic material for the zygote
-larger than sperm - does not have to move as it contains a large number of nutrients in it’s cytoplasm
-zona pellucida - hardens when one sperm fuses with the ovum membrane to prevent polyspermy

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23
Q

describe the cortical reaction

A

-occurs when the sperm fuses with the ovum membrane and sperm nucleus enters ovum
-chemicals released by cortical granules trigger the zona pellucida to harden to prevent polyspermy

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24
Q

describe the acrosome reaction

A
  1. sperm attracted to ovum because of chemicals released from it
  2. acrosome in sperm head swells
  3. acrosome fuses with sperm cell surface membrane
  4. digestive enzymes released
  5. zona pellucida broken down
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25
Q

describe steps of fertilisation

A
  1. sperm reach the ovum
  2. chemicals released from follicle cells around ovum trigger acrosome reaction
  3. acrosome swells, fusing with sperm cell surface membrane
  4. digestive enzymes in acrosome are released
  5. enzymes digest through follicle cells and zona pellucida around the ovum
  6. sperm fuses with ovum membrane
  7. sperm nucleus enters the ovum
  8. enzymes released from lysosomes in the ovum thicken the zona pellucida to prevent polyspermy
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26
Q

Describe a light microscope

A

-uses light to form an image
-do not have a high resolution so you cannot see smaller organelles through it

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27
Q

Describe an electron microscope

A

-use beams of electrons to form an image
-have a higher resolution so image is more detailed
-specimen has to be dead to view it

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28
Q

What does meiosis produce?

A

gametes

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29
Q

Describe the meiosis process

A

-DNA replicates so there are two identical copies of each chromosome (chromatids)
-DNA condenses and two sister chromatids join to form an X shape, joined by a centromere
-Chromosomes arrange into homologous pairs (pairs of matching chromosomes)
-First division - homologous pairs are separated, halving the chromosome number
-Second division - pairs of sister chromatids are separated
-4 genetically different haploid daughter gametes produced

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30
Q

Define homologous chromosomes

A

chromosomes that carry the same gene in the same position and both are the same shape
-you can inherit different alleles or the same allele from your mother and father on a homologous chromosome

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31
Q

Two processes leading to genetic variation in meiosis?

A

Crossing over and independent assortment

32
Q

Describe crossing over

A

1) homologous pairs come together and pair up
2) two of the chromatids in each twist around each other
2.5) the point of contact is the chiasma
3) twisted bits break off original chromatid and rejoin on another chromatid, recombining their genetic material
4) chromatids now still have same genes but a different combination of alleles
5) four new cells from meiosis contain chromatids with different alleles
6) chiasma can occur in multiple different places

33
Q

Describe independent assortment

A

-when chromosomes line up on the spindle at equator, we cannot predict the combinations of maternal and paternal chromosomes that will end up in each daughter cell
-different combinations of maternal and paternal chromosomes end up in different cells
-genes with loci on different chromosomes end up randomly distributed in the gametes

34
Q

define locus

A

position of a gene on a chromosome

35
Q

when are genes linked?

A

when they have loci on the same chromosome - they are less likely to be separated during independent assortment and cross over
-the closer together they are, the more closely linked they are (cross over is less likely to split them up)

36
Q

when is a characteristic sex-linked?

A

when the locus of the allele that codes for it is on a sex chromosome

37
Q

why are males more likely to display recessive phenotypes?

A

-males = XY and females = XX
-Y chromosome is smaller than X chromosome and carries few genes
-most genes are X-linked (carried on X chromosome)
-males only have 1 X chromosome - they’ll have one allele for sex-linked genes so only one copy
-if this copy is recessive, they will express this characteristic and there is only one copy
-examples of X-linked disorders are colour blindness and haemophilia

38
Q

why is mitosis important?

A

-growth of multicellular organisms
-repairing damaged tissues
-asexual reproduction

39
Q

Describe interphase

A

-period of cell growth and DNA replication
-G1 - organelles replicate, respiration, protein synthesis, cell elongates
-synthesis - DNA replication
-G2 - proteins for cell division are made, energy is stored

-length of G1 phase is variable whilst the other two are fairly constant
-in interphase, individual chromosomes are unravelled to allow access to genetic material to be replicated

40
Q

Explain why the pattern of inheritance on sex chromosomes is different (2)

A

-X chromosome carries {genes/loci} not present on Y chromosome (1)
-males only have one{copy/allele} of some genes (1)
-if 1 allele only is inherited, it will be expressed (1)

41
Q

Describe the organization of DNA in chromosomes

A
  1. DNA is its double helix (2nm)
  2. DNA winds around histone proteins (nucleosome) (11nm)
  3. DNA and histone proteins coil to form chromatin fibre (polynucleosome) (30nm)
  4. Chromatin fibre attaches to a protein scaffold to form loops (300nm)
  5. Protein scaffolding is folded to produce the usual condensed chromosome structure (1400nm)
42
Q

describe prophase

A

-chromosomes condense and become visible - each one becomes visible chromatids
-centrioles (release spindles) move to cell poles
-nuclear envelope disintegrates
-nucleolus disappears

43
Q

describe metaphase

A

-centromeres and chromosomes attach to spindles at equator

44
Q

describe anaphase

A

-centromeres split
-spindles shorten so centromere halves and chromatids are pulled to the poles
-one chromatid of each chromatid is moved to the poles

45
Q

describe telophase

A

-last stage of mitotic division
-reverse of prophase
-nuclear envelope reforms
-chromosomes unravel
-nucleolus reappears
-two sets of genetic material in separate nuclei

46
Q

describe cytoplasmic division / cytokinesis

A

-final reorganisation
-cell surface membrane constricts around cell center
-protein filament ring on the inside surface of the cell membrane contract (by actin and myosin) until the cell divides into two

47
Q

describe cell formation in plants

A

-instead of cytokinesis, the synthesis a new cell plate
-Golgi vesicles carry new cell wall material along microtubules
-vesicles fuse to form new cell plate

48
Q

define pluripotency

A

pluripotent stem cells are embryonic stem cells that can differentiate into any types of cells except cells that form the placenta and the umbilical cord

49
Q

define totipotency

A

totipotent stem cells - embryonic stem cells that can differentiate into any types of cells including cells that form the placenta and the umbilical cord (extra embryonic stem cells)

50
Q

define stem cell

A

a cell that can divide via mitosis an unlimited amount of times

51
Q

define multipotency

A

multipotent stem cells are adult stem cells that are no longer pluripotent as they only differentiate into certain types of cells

52
Q

what are the pros and cons of using stem cells in medical therapies?

A

PROS
-they could save lives (for example, people don’t have to wait as long for organ transplants)
-could improve the quality of life (replace damaged cells in eyes of people who are blind)
-can treat many conditions
-reduced risk of rejection

CONS
-many ethical issues are associated with embryonic stem cells
-their nature is still not fully understood
-obtaining adult stem cells may be simple, but is not comfortable
-adult stem cells have less potency

53
Q

describe the ethical issues that arise with the use of stem cells

A

-IVF procedure results in the destruction of an embryo that’s viable
-belief that at the moment of fertilisation the embryo is an individual that has a right to life, so its wrong to destroy an embryo
-belief that only adult stem cells should be used even if they have reduced potency

54
Q

describe how stem cells become differentiated

A

-there is a stimulus such as a chemical or a hormone
-this leads to some genes being switched on / active and some being switched off / inactive
-mRNA is only transcribed from the active genes
-(active gene’s) mRNA is translated into proteins
-proteins modify the cell and determine the cell structure and function
-modification and changes to the cell cause the cell to become specialised (differentiate).
-changes are irreversible

55
Q

Describe tissues, organs and systems and their formation

A

-A tissue is a group of cells that work together to perform a particular function
-Different tissues can group together to form organs
-An organ is a group of tissues working together to perform a particular function
-Different organs work together to form organ systems
-An organ system is a group of organs working together to perform a particular function

56
Q

Describe how cells are organised into tissues

A

-specialised cells group themselves into clusters
-cells have specific recognition proteins on their cell surface membranes, which are known as adhesion molecules
-adhesion molecules help cells recognise other like cells and stick to them
-the exposed section of one recognition protein binds to complementary recognition proteins on the adjacent like cell, forming a desmosome
-the recognition proteins that are made/synthesised by a cell determines which cells it can attach to, even if the cluster disbands

57
Q

how does genotype and environment affect phenotype?

A

-changes in genotype ad environment cause phenotypic variation (can be a combination of both factors)
-Phenotype = Genotype + Environment
-some phenotypes are affected by multiple different alleles/genes at many different loci as well as the environment (phenotypes with continuous variation). this can be influenced by polygenes with an additive effect

58
Q

how does genetic variation affect phenotype?

A

Genetic variation - small differences in DNA base sequences between individual organisms within a species population
-genetic variation is inherited from generation to the next through alleles, resulting in phenotypic variation.
-the phenotype of an organism and its characteristics can be controlled by a single gene - this is known as monogenic - discontinuous variation
-other characteristics are controlled by several genes - these characteristics are polygenic - continuous variation
-the different alleles present at a specific gene locus can determine an organisms phenotype

59
Q

how can the environment affect phenotype?

A

-different environments have different environmental conditions, therefore different selection pressures too
-this means that allele frequency changes as organism grow and adapt in response to their environment
-also the environment can hinder organisms reaching the full potential of their genotype. for example, a plant with a tall genotype cannot get there if theres no water or minerals.
-variation in phenotype solely by environmental factors cannot be inherited by offspring, unless there are changes to the genetics of the parent gamete.

60
Q

Describe the effect of DNA methylation on a gene

A

-the chemical addition of -CH3 groups, as epigenetic tags, to cytosine
-DNA methylation is independent and does not influence the methylation of another section of gene
-causes the inactivation of genes
-it suppresses the transcription of the affected gene by inhibiting the binding of transcription factors and enzymes needed for transcription
-gene is said to be repressed or inactive, so its switched off
-it can be triggered by environment and lifestyle factors

61
Q

define ‘epigenetics’

A

The control of gene expression by factors other than an individual’s DNA sequence
-involves the switching-on and switching-off of genes, but without changing the actual genetic code

62
Q

Describe the effect of histone modification on a gene

A

-addition of acetyl groups -COCH3 to lysine amino acids on histone proteins
-USUALLY, positively charged lysine R group forms ionic bonds with negative phosphate backbone of DNA, so DNA coils tightly around the histone protein core
-acetylation to lysine removes the positive ion so bond between histone and DNA is gone
-DNA becomes less tightly wrapped
-transcription factors bind more easily, gene expression can occur
-gene is activated
-removing acetyl groups makes DNA wrap more tightly around histone so transcription is inhibited again, so no gene expression

63
Q

describe how epigenetic changes can be inherited

A

-epigenome is heritable
-when a cell is replicated and divides, epigenetic changes affecting gene expression in DNA can be passed on to daughter cells
-sometimes methyl groups can be left on the DNA during gamete production and are then present in the sperm and egg cells
-same genes are active or switched off in daughter cell
-if there was an epigenetic change because of an environmental factor, it would be beneficial for the daughter cells to be better adapted too
-epigenetics can be passed on at a cellular or whole organism level

64
Q

Describe the lac operon model

A

-controls the production of lactase (beta galactosidase)
-lactase breaks down lactose so it can be used as energy in bacteria
-lact

Wase is only synthesised when lactose is present so energy and material is not wasted

Structure of lac operon:
In this order: Promoter region, Operator region, structural gene lacZ (codes for lactase), lacY and lacA structural genes
-has a regulatory gene lacl that codes for the lac repressor protein
-has a promoter for the regulatory gene
-the lac repressor protein has two binding sites where it can bind to the operator region on the lac operon and also where lactose (effector molecule) can bind to it to get it off of the lac operon operator
-when it binds to the operator region it prevents transcription because RNA polymerase cannot attach and start transcription
-when lactose binds to it, the lac repressor protein shape changes so it cant bind to the operator region anymore, so transcription occurs

WHEN LACTOSE IS ABSENT
-regulatory gene is transcribed and translated so the lac repressor protein is produced
-lac repressor protein binds to operator region, before lacZ region
-RNA polymerase cannot bind to promoter region
-no transcription of structural genes
-no lactase enzyme synthesized

WHEN LACTOSE IS PRESENT
-bacteria takes in lactose
-lactose binds to 2nd binding sited on the lac repressor protein, so the shape gets distorted
-repressor cannot bind to the operator site
-RNA polymerase binds to promoter region and transcription happens
-mRNA from all structural genes translated
-lactase is produced and lactose is broken down for energy

65
Q

Describe the process of melanin production due to UV radiation

A

LOW UV LIGHT EXPOSURE
-melanocyte-stimulating hormone (MSH) are produced by pituitary gland
-receptors for MSH on melanocyte cells place it into the cells and melanin is made
-melanin is placed into melanosomes
-melanosomes are transferred to skin cells
-melanosomes collect around the nucleus and protect it from damage by UV light

-in high exposure to UV light, the scale of which all of this happens is much greater
-UV light damage to the nucleus lead to mutations in DNA, which could lead to skin cancer

66
Q

explain how methylation of the oncogene affects cancer development

A

-oncogenes code for the proteins that stimulate the transition between stages of the cell cycle
-less methylation leads to the cell cycle being continually active and never ending
-leads to excessive cell division and a tumour

67
Q

explain how methylation of the tumour suppressor genes affects cancer development

A

-produce suppressor genes that stop the cycle
-more methylation means theres no break on the cell cycle
-uncontrollable cell division
-rate of transcription is inhibited as DNA is more tightly wrapped around histones.
-this means the gene to stop the cell cycle cannot be synthesised.

68
Q

explain the uneven distribution of fur colour in a siamese cat

A

-face, ears, tail and paws of the cat are darker and they have a lower body temperature
-tyrosinase enzyme is denatured at normal body temperature due to a mutation.
-dihydroxyphenylalanine not synthesised as tyrosine is not broken down
-melanin is not formed at normal body temperature as a result
-gene for darker fur is deactivated
-at colder temperatures, tyrosinase is present and catalyses synthesis of DHPL
-melanin pigment is produced
-gene for darker fur is activated at colder temperatures, due to a mutation.

69
Q

define allele

A

a different form of the same gene. dominant or recessive alleles can be inherited from parents by offspring

70
Q

define phenotype

A

the physically expressed traits of an organism

71
Q

define asexual reproduction

A

The production of genetically identical offspring from one parent through the process of mitosis.

72
Q

define sex linkage

A

An allele which is found on a sex chromosome and so its expression is determined on the gender of the organism.

73
Q

define zona pellucida

A

The tough outer layer of the egg cell which is composed of glycoproteins and is used to prevent multiple sperm cells from fertilizing the egg.

74
Q

define differential gene expression

A

The process of switching on or off genes to control functions within a cell by varying the production of proteins.

75
Q

define DNA methylation

A

The epigenetic modification of DNA by the addition of a methyl group which reduces transcription.

76
Q

define histone modification/acetylation

A

The epigenetic modification of histone proteins by the addition of an acetyl group which loosens the DNA coiling around the histone protein and increases transcription.

77
Q

define polygenic inheritance

A

The inheritance of multiple different alleles at multiple loci that control a single phenotype.

Alevel Bio (8 decks)

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