B13 Reproduction

Question 1

how do cells divide in asexual reproduction

Answer 1

mitosis

Question 2

how do gametes form

Answer 2

meiosis

Question 3

what is meiosis used for in plants

Answer 3

making egg and pollen cells

Question 4

how do gametes introduce variation

Answer 4

each of the 4 gametes produced from 1 cell are different and contain random mixtures of the original chromosome which provides variation

Question 5

what are advantages of asexual reproduction (2)

Answer 5

only one parent needed which is time and energy efficient

rapidly produces large numbers of identical offspring

Question 6

what is an advantage of sexual reproduction

Answer 6

variation which gives a survival advantage if the environment changes

Question 7

what is a disadvantage of asexual reproduction

Answer 7

no variation is a disadvantage if the environment changes as organism is unable to adapt

Question 8

what is a disadvantage of sexual reproduction

Answer 8

takes time and energy to find a mate or spread gametes

slower than asexual reproduction

Question 9

why do fungi reproduce sexully and asexually

Answer 9

they normally reproduce asexually when fungal spores go through mitosis but when conditions are not good eg dry, 2 hyphae from different fungi join and their nuclei fuse so the new hypha has 2 sets of chromosomes this then undergoes meiosis to make haploid spores each with only one set of chromosomes

Question 10

how are flowers adapted for sexual reproduction

Answer 10

either adapted to attract animal pollinators or make it easy for their pollen to be carried by the wind and caught by another flower

Question 11

how do malaria parasites reproduce

Answer 11

sexually in mosquitos and asexually in human host

Question 12

what do genes code for

Answer 12

a particular sequence of amino acids to make a specific protein that make up different specialised cells that form tissues including the enzymes that control cell chemistry

Question 13

what is DNA made up of

Answer 13

combinations of 4 different chemical bases (monomers)

Question 14

what is the genome of an organism

Answer 14

the entire genetic material of that organism including all chromosomes and genetic material in the mitochondira

Question 15

where does mitochondrial dna come from

Answer 15

inherited from the mother as it comes from the mitochondria in the egg

Question 16

why are bacteria and virus genomes sequenced

Answer 16

helps to identify causes of disease very rapidly and choose the correct treatment

Question 17

what is a gene

Answer 17

a small section of dna on a chromosome. Each gene codes for a articular sequence of amino acids to make a specic protein

Question 18

what is a nucleotide

Answer 18

combination of a sugar, base and a phosphate

Question 19

how do nucleotides help code for amino acids

Answer 19

nucleotides are grouped into threes and each set of 3 bases codes for a particular amino acid

Question 20

dna in the nucleus controls protein synthesis but proteins are synthesised in the cytoplasm- explain this

Answer 20

genes in the dna produce a template for the protein which reflects the sequence of bases in the dna but is small enough to leave the nucleus through pores
template binds to the surface of a ribosome
the cytoplasm contains carrier molecules which are each attached to a specific amino acid
the carrier molecules attach to the template
amino acids are joined together to form a specific protein
carrier molecules keep bringing amino acids to add to the growing protein chain until the template is completed

Question 21

what happens once the protein chain is completed

Answer 21

the molecule folds up to form a unique shape that will enable it to carry out its cell functions eg for an enzyme it will form the shape of the active site

Question 22

what does the non coding part of dna do

Answer 22

involved in the switching on or off of genes or parts of genes

Question 23

what does it mean when a gene is expressed

Answer 23

when it codes for a protein that is synthesised in the cell

Question 24

what does variation in the non coding parts of dna cause

Answer 24

has an effect on how genes are expressed which affects phenotype (physical appearance)

Question 25

what happens when there is a mutation in the coding DNA

Answer 25

protein formed is altered so slightly that apearance and function is not changed

Question 26

what happens when there is a mutation in the non coding dna

Answer 26

can affect which genes are switched on and off which can have a big effect on the phenotype of the organism

Question 27

what is an allele

Answer 27

different versions of the same gene. You have 2 allleles for each gene- one from each parent

Question 28

define homozygote

Answer 28

an individual with 2 identical alleles for a characteristic eg BB or bb

Question 29

define heterozygote

Answer 29

an individual with different alleles for a characteristic eg Bb

Question 30

define genotype

Answer 30

what alleles the person has for that gene

Question 31

define phenotype

Answer 31

what the individual looks like eg eye colour, dimples

Question 32

what is a dominant allele

Answer 32

an allele that controls the characteristic when there is just one allele present

Question 33

what is a recessive allele

Answer 33

an allele that must have 2 copies present to control the characteristic

Question 34

what are the female sex chromosomes

Answer 34

XX

Question 35

what are the male sex chromosomes

Answer 35

XY

Question 36

what is an inherited disorder

Answer 36

result of a change in the bases or coding of genes and can be passed from parent to child

Question 37

what is polydactyly

Answer 37

when a baby is born with extra fingers or toes formed by a dominant allele so if you are heterozygous you have a 50% chance of passing it onto your child and if you are homozygous you have a 100% chance

Question 38

what is huntingtons disease

Answer 38

a dominant genetic disorder symptoms develop in middle ages affects nervous system and can cause death

Question 39

how is cystic fibrosis inherited

Answer 39

passed on by a recessive allele so both parents must be carriers

Question 40

what is cystic fibrosis

Answer 40

disorder of cell membranes that affects movement of certain substances so mucus made by cells becomes very thick lungs can become clogged and stop working properly pancreas cannot make and secrete enzymes properly as tubes are blocked causes infertility

Question 41

what is the treatment for cystic fibrosis

Answer 41

no cure but physiotherapy and antibiotics used to help clear lungs of mucus and infection enzymes are used to replace ones that pancreas can't make

Question 42

what is amniocentisis

Answer 42

carried out at 15-16 weeks of pregnancy involves taking some fluid from around the developing fetus which contain fetal cells and can then be used for embryonic genetic screening

Question 43

what is chronic villus sampling of embryonic cells

Answer 43

done between 10-12 weeks of pregnancy by taking a small sample of tissue from the developing placenta- provides fetal cells to screen

Question 44

what are the risks of embryonic screening

Answer 44

miscarriage

Question 45

how is screening carried out

Answer 45

dna is separated from embryonic cell and tested

Question 46

what are concerns about embryonic screening

Answer 46

can sometimes give a false positive or false negative couple have to make the difficult decision of whether or not to terminate pregnancy screening is expensive could give a rise to 'designer babies'