3.1/1.6

Question 1

what is a gene

Answer 1

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.

Question 2

what is a locus (loci)

Answer 2

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

Question 3

homologous chromosomes

Answer 3

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.

Question 4

what are alleles

Answer 4

various specific forms of a gene

Question 5

how much can alleles differ from eachother

Answer 5

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

Question 6

homologous pair relationship with alleles

Answer 6

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

Question 7

where are alleles from

Answer 7

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

Question 8

what are mutations

Answer 8

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

Question 9

what are the 3 typess of mutations

Answer 9

neutral

harmful

benefecial

Question 10

neutral mutations

Answer 10

neutral or ‘silent’

i.e they have no observable effect on the orgainism

Question 11

harmful mutations

Answer 11

evident because they may alter the survival capacity of the organism

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

Question 12

benefecial mutations

Answer 12

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

Question 13

causes of mutations

Answer 13

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

Question 14

spontaneous mutations

Answer 14

arise from errors in DNA replication.

different genes mute at different rates

Question 15

induced mutations

Answer 15

can be induced by mutagens

Question 16

what are mutagens

Answer 16

envriomental factors that cause a change in DNA

Question 17

examples of mutagens

Answer 17

radiation
viruses
microorganism
enviromental poisons and irritants
alcohol and diet

Question 18

what do mutations locations determine

Answer 18

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

Question 19

if mutations occur in somatic cell will they be inherited

Answer 19

no

Question 20

if mutations occur in gametic cell will they be inherited

Question 21

what are the two types of mutation

Answer 21

gene mutations (change in base sequences)

chromosomes mutations (affects number of chromosomes)

Question 22

gene mutations

Answer 22

change in base sequences in DNA for a single gene

may produce a new allele of a gene

Question 23

What is a point mutation

Answer 23

Gene mutations involving a single nucleotide

Question 24

Playing you DNA sequence may result in what

Answer 24

A new sequence of the amino acids constituting a protein

Question 25

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

Answer 25

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

Question 26

Finish the sentence Even with a change in amino acid sequence...

Answer 26

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

Question 27

A change THAT FORMS the 'stop' codon good what to the polypeptide

Answer 27

It would stop without of the polypeptide at the wrong place

Question 28

a change IN a 'stop' codon would cause what

Answer 28

It would cause the polypeptide to go on and on

Question 29

Eddie or taking away a nucleotide causes what

Answer 29

A reading frame shift They continued to read mRNA nucleotides three at a time Frameshift mutations are usually lethal

Question 30

Haemoglobin molecules are made up of what

Answer 30

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

Question 31

What is sicko cell anaemia caused by

Answer 31

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

Question 32

What is a Genome

Answer 32

The whole of the genetic information of an organism This includes codeine and non-Coding regions

Question 33

The genome size

Answer 33

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

Question 34

Genome sizes in different haploid genome

Answer 34

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)

Question 35

Eukaryote chromosomes

Answer 35

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

Question 36

Prokaryote chromosome

Answer 36

prokaryotes have one chromosome consisting of a circular DNA molecule Some prokaryotes also have plasmids but eukaryotes do not

Question 37

what are autosomes

Answer 37

posture songs are chromosomes that do not determine sex

Question 38

Diploid nuclei had pairs of what

Answer 38

Homologous chromosomes

Question 39

what is mitosis

Answer 39

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

Question 40

what happens to chro mosomes during mitosis

Answer 40

they condense by supercoiling

Question 41

cytokinesis occurs...

Answer 41

after mitosis and is different in plant and animal cells

Question 42

cytokinesis differences in plants and animal cells

Answer 42

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

Question 43

how to determine a mitotic index

Answer 43

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

Question 44

what is interphase

Answer 44

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

Question 45

how do cells grow

Answer 45

by adding material to their cell

Question 46

cell divison

Answer 46

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

Question 47

cell divison occurs under what 3 circumstances

Answer 47

development and growth cell replacement asexual reproduction

Question 48

development and growth

Answer 48

the no. of cells in an oargainism increases by mitosis

Question 49

cell replacement

Answer 49

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

Question 50

asexual reproduction

Answer 50

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

Question 51

what is interphase

Answer 51

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

Question 52

interphase process

Answer 52

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

Question 53

interphase - G1

Answer 53

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

Question 54

interphase -S

Answer 54

S – Synthesis stage in which DNA is replicated

Question 55

interphase - G2

Answer 55

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

Question 56

Prophase:

Answer 56

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

Question 57

Metaphase:

Answer 57

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)

Question 58

Anaphase:

Answer 58

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

Question 59

Telophase:

Answer 59

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

Question 60

Cytokinesis in animal cells

Answer 60

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

Question 61

cytokinesis in plant cells

Answer 61

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

Question 62

Haploid nuclei have what

Answer 62

One chromosome of each pair

Question 63

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

Answer 63

Chromosomes

Question 64

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

Answer 64

23 pairs

Question 65

What is the diploid number

Answer 65

The total number of homologous chromosomes Is given the symbol number 2n In humans, 2n=46

Question 66

What is the haploid number

Answer 66

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

Question 67

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

Answer 67

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

Question 68

what is cancer caused by

Answer 68

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

Question 69

how do cancerous cells form

Answer 69

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

Question 70

the four features of cancerous cells

Answer 70

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

Question 71

apoptosis

Answer 71

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

Question 72

what is a tumour

Answer 72

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