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Biology- IB > 3.1/1.6 > Flashcards

3.1/1.6 Flashcards

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1
Q

what is a gene

A

a heritable factor that consists of a length of DNA and influences a specific characteristic.

they are lengths of DNA that code to make a protein.

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2
Q

what is a locus (loci)

A

a position on a chromosome where a gene for a particular trait is located

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3
Q

homologous chromosomes

A

chromosomes that have the same:
genes,
size,
placement for the centromere
gene loci in the same sequence
pattern of banding

X and Y chromosomes have an unmatched region on the X chromosome as the Y is shorter.

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4
Q

what are alleles

A

various specific forms of a gene

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5
Q

how much can alleles differ from eachother

A

one or only a few bases

each allele will show a slight difference in base orders.
this is enough to alter the protein so it is different slightly

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6
Q

homologous pair relationship with alleles

A

the homologous pair carry alternative forms of a gene which are called alleles

homologous chromosomes carry the same sequence of gene but not necessarily the same alleles of those genes

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7
Q

where are alleles from

A

one from the mother’s egg
one from the father’s sperm

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8
Q

what are mutations

A

alterations in the DNA of chromosomes that is not immediately and properly repaired.

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9
Q

what are the 3 typess of mutations

A

neutral

harmful

benefecial

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10
Q

neutral mutations

A

neutral or ‘silent’

i.e they have no observable effect on the orgainism

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11
Q

harmful mutations

A

evident because they may alter the survival capacity of the organism

e.g. sickle cell anemia, cystic fibrosis, albinism

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12
Q

benefecial mutations

A

benefecial form the basis for evolution. any mutation that improves survival of an organism will of an organism will be passed on

e.g. disease resistance, chlorosterol tolernance, antibiotic resistance in bacteria

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13
Q

causes of mutations

A

may occur randomly and spontaneously.
may also be induced by enviromental factors

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14
Q

spontaneous mutations

A

arise from errors in DNA replication.

different genes mute at different rates

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15
Q

induced mutations

A

can be induced by mutagens

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16
Q

what are mutagens

A

envriomental factors that cause a change in DNA

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17
Q

examples of mutagens

A

radiation
viruses
microorganism
enviromental poisons and irritants
alcohol and diet

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18
Q

what do mutations locations determine

A

whether it will or will not be inherited

most mutations occur in somatic cells and are not inherited

gametic mutations occur in the cells of the gonads( which produce sperm and eggs) and may be inherited

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19
Q

if mutations occur in somatic cell will they be inherited

A

no

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20
Q

if mutations occur in gametic cell will they be inherited

A
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21
Q

what are the two types of mutation

A

gene mutations (change in base sequences)

chromosomes mutations (affects number of chromosomes)

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22
Q

gene mutations

A

change in base sequences in DNA for a single gene

may produce a new allele of a gene

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23
Q

What is a point mutation

A

Gene mutations involving a single nucleotide

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24
Q

Playing you DNA sequence may result in what

A

A new sequence of the amino acids constituting a protein

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25
Q

Because of the degeneracy (corruption) in the genetic code what may happen

A

Not all changes in any DNA sequence will result in a new sequence of amino acids

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26
Q

Finish the sentence

Even with a change in amino acid sequence…

A

protein function may be unaffected (the mutation is neutral).

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27
Q

A change THAT FORMS the ‘stop’ codon good what to the polypeptide

A

It would stop without of the polypeptide at the wrong place

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28
Q

a change IN a ‘stop’ codon would cause what

A

It would cause the polypeptide to go on and on

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29
Q

Eddie or taking away a nucleotide causes what

A

A reading frame shift

They continued to read mRNA nucleotides three at a time

Frameshift mutations are usually lethal

30
Q

Haemoglobin molecules are made up of what

A

Two alpha (α) chains and two beta (β) chains linked together

31
Q

What is sicko cell anaemia caused by

A

An autosomal recessive mutation on chromosome 11

This results in the substitution of a single nucleotide base in the gene encoding for the Beta chain of the haemoglobin in which mutates GAG to GUG which changes the amino acid from glutamic acid to Valine.

This changes the structure of the haemoglobin molecule

Normal red cells containing normal haemoglobin (soluble)
Maximises oxygen-carrying.

sickle cell containing mutant haemoglobin (less soluble) are less efficient at carrying oxygen

The haemoglobin of clusters together to form fibre which deforms the red blood cells into a circle shape

32
Q

What is a Genome

A

The whole of the genetic information of an organism

This includes codeine and non-Coding regions

33
Q

The genome size

A

The genome size is the total number of DNA base pairs in one copy of other haploid Genome

Comparison of two know the size in T2 phage, Escherichia coli, drsophila melanogastar, homo sapians and Paris japonica

34
Q

Genome sizes in different haploid genome

A

Virus T2 phage - 5kb
Escherichia coli (bacteria) 4,600,000kb (4.6 mb) with 4200 genes
drsophila melanogastar (fruitfly) (150 Gb) with 20, 000 genes
Paris japonica 150, 000, 000, 000 (150Gb) (largest plant genome)
Protopterus aetgeopicus 130, 000, 000 (130Gb) (Long fish, largest animal genome)

35
Q

Eukaryote chromosomes

A

They usually exist as homologous pairs

are typically two of each kind in the somatic (body) cells of higher plants and animals

The exception to the homologous pairs being the same are the sex chromosomes

Human males have 22 pairs of autosomes (chromosomes other than sex chromosomes) Plus X and Y

Females have 22 pairs of autosomes plus X and X

Chromosomes usually appear as single strands. however, just before cell division the DNA makes a copy of itself (replication)
At this time they have a double-stranded appearance consisting of two sister chromatids connected at the centromere

Eukaryote chromosomes are linear DNA molecules associated with histone proteins

Homologous chromosomes carry the same sequence of genes but not necessarily the same alleles of those genes

In a eukaryotic species, there are different chromosomes that carry different genes

Sex is determined by six chromosomes

36
Q

Prokaryote chromosome

A

prokaryotes have one chromosome consisting of a circular DNA molecule

Some prokaryotes also have plasmids but eukaryotes do not

37
Q

what are autosomes

A

posture songs are chromosomes that do not determine sex

38
Q

Diploid nuclei had pairs of what

A

Homologous chromosomes

39
Q

what is mitosis

A

the divison of the nucleus into two genetically identical daughter nuclei

cells follow a pattern follow a pattern for at least part of their lie: growing first, then dividing to produce two new cells

40
Q

what happens to chro mosomes during mitosis

A

they condense by supercoiling

41
Q

cytokinesis occurs…

A

after mitosis and is different in plant and animal cells

42
Q

cytokinesis differences in plants and animal cells

A

animal cells lack a cell whereas plant cells do have a cell wall

in plants a cell plate begins to grow which will become the new cell wall

in animals the ell membranes on opposite sides become pinched which forms a cleavage furrow until the two sides touch

in plants the cell plate extends outwards and fuses with the cell wall, dividing the cell into two distinct daughter cells
Because this separation originates in the centre and moves laterally

43
Q

how to determine a mitotic index

A

determines how % cells in a group of cells are undergoing mitosis at a given time

                       number of cells in mitosis  mitotic index = -------------------------------------------- X 100
                      total number of cells
44
Q

what is interphase

A

a very activecell cycle phase with many processes occurring in the nuclear and cytoplasm

45
Q

how do cells grow

A

by adding material to their cell

46
Q

cell divison

A

cells follow a pattern follow a pattern for at least part of their lie: growing first, then dividing to produce two new cells

cells grow by adding materials to their cell
cells divide by mitosis- a parent cell divides into 2 or more daughter cells

cell division is usually a small segment of a larger cell cycle

47
Q

cell divison occurs under what 3 circumstances

A

development and growth

cell replacement

asexual reproduction

48
Q

development and growth

A

the no. of cells in an oargainism increases by mitosis

49
Q

cell replacement

A

cells in some body areas are constantly gotten rid of and replaced by new cells
the new ones are formed by mitosis and are therefore daughter cells (exact copies) of the replaced cells

50
Q

asexual reproduction

A

some organisms reproduce asexually in bacteria and negative reproduction in plants, producing genetically similar offspring

51
Q

what is interphase

A

Interphase is an active period in the cell cycle when many metabolic reations occur

Many events need to occur in interphase to prepare the cell for successful division

52
Q

interphase process

A

DNA is present as uncondensed chromatin (not visible under microscope)
DNA is contained within a clearly defined nucleus
Centrosomes and other organelles have been duplicated
Cell is enlarged in preparation for division

D-DNA replication – DNA is copied during the S phase of interphase
O-Organelle duplication – Organelles must be duplicated for twin daughter cells
C-Cell growth – Cytoplasmic volume must increase prior to division
T-Transcription / translation – Key proteins and enzymes must be synthesised
O-Obtain nutrients – Vital cellular materials must be present before division
R-Respiration (cellular) – ATP production is needed to drive the division process

Mnemonic: DOCTOR

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|/ |/

53
Q

interphase - G1

A

G1 – First intermediate gap stage in which the cell grows and prepares for DNA replication

54
Q

interphase -S

A

S – Synthesis stage in which DNA is replicated

55
Q

interphase - G2

A

G2 – Second intermediate gap stage in which the cell finishes growing and prepares for cell division

56
Q

Prophase:

A

DNA supercoils and chromosomes condense (becoming visible under microscope)
Chromosomes are comprised of genetically identical sister chromatids (joined at a centromere)
Paired centrosomes move to the opposite poles of the cell and form microtubule spindle fibres
The nuclear membrane breaks down and the nucleus dissolves

57
Q

Metaphase:

A

Microtubule spindle fibres from both centrosomes connect to the centromere of each chromosome
Microtubule depolymerisation causes spindle fibres to shorten in length and contract
This causes chromosomes to align along the centre of the cell (equatorial plane or metaphase plate)

58
Q

Anaphase:

A

Continued contraction of the spindle fibres causes genetically identical sister chromatids to separate
Once the chromatids separate, they are each considered an individual chromosome in their own right
The genetically identical chromosomes move to the opposite poles of the cell

59
Q

Telophase:

A

Once the two chromosome sets arrive at the poles, spindle fibres dissolve
Chromosomes decondense (no longer visible under light microscope)
Nuclear membranes reform around each chromosome set
Cytokinesis occurs concurrently, splitting the cell into two

60
Q

Cytokinesis in animal cells

A

After anaphase, microtubule filaments form a concentric ring around the centre of the cell
The microfilaments constrict to form a cleavage furrow, which deepens from the periphery towards the centre
When the furrow meets in the centre, the cell becomes completely pinched off and two cells are formed
Because this separation occurs from the outside and moves towards the centre, it is described as centripetal

61
Q

cytokinesis in plant cells

A

After anaphase, carbohydrate-rich vesicles form in a row at the centre of the cell (equatorial plane)

The vesicles fuse together and an early cell plate begins to form in the middle of the cell

The cell plate extends outwards and fuses with the cell wall, dividing the cell into two distinct daughter cells

Because this separation originates in the centre and moves laterally, it is described as centrifugal

62
Q

Haploid nuclei have what

A

One chromosome of each pair

63
Q

The number of ———— is a characteristic feature of members of a species

A

Chromosomes

64
Q

As humans there are how many pairs of chromosomes in all somatic (body) cells

A

23 pairs

65
Q

What is the diploid number

A

The total number of homologous chromosomes

Is given the symbol number 2n
In humans, 2n=46

66
Q

What is the haploid number

A

The number of chromosomes in a single set

Is given the symbol n

This is the number found in the gamates of animals and the spores of plants and is usually equal to half the number of chromosomes found in the body cells of the higher organisms

67
Q

John cairn’s Technique for measuring the length of DNA molecules

A

John Cairns (1963) was it the first to determine the length of DNA molecules using a technique called autoradiography

He grew bacterial cells on thymidine; a deoxyribonucleotide made from heavy H^3 hydrogen isotope. The radioactive deoxyribonucleotide was only taken up by the replication DNA. He then reviewed these newly built radioactive strands using autoradiography

68
Q

what is cancer caused by

A

gene mutations

cells in the body become abnormal and grow of control as a result of uncontrolled cell divison and growth

69
Q

how do cancerous cells form

A

normal cells divide as many times as they needed and then stop.
they attach to other cells and stay in place in tissues
they commit cell suicide when they are no longer needed

cells become cancerous when they lose the ability to stop dividing, to attach to other cells, to stay where they belong and to die at the proper times

70
Q

the four features of cancerous cells

A

cells become cancerous when they lose the ability to stop dividing, to attach to other cells, to stay where they belong and to die at the proper times

71
Q

apoptosis

A

cell suicude

normal cells commit cell suicide (apoptosis) when they are no longer needed

72
Q

what is a tumour

A

a group of cells that has resulted from uncontrolled cell division and growth is called a tumour

Biology- IB (10 decks)

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