Reproduction and inheritance Flashcards
describe the differences between sexual and asexual reproduction
1) asexual involves mitosis
2) asexual creates identical offspring with no variation in the population
3) sexual involves meiosis
4) sexual creates genetically different offspring with variation in the population
5) sexual involves the fusion of male and female gametes
what is fertilisation
the fusion of a male and female gamete to form a zygote (which undergoes cell division and develops into an embryo
describe the structure of an insect pollinated plant
1) brightly coloured petals
2) scented flowers + nectaries
3) big sticky pollen grains
4) sticky stigma
describe the structure of a wind pollinated plant
small dull petals no nectaries lots of light pollen grains long filament that hangs outside the flower large feathery stigma outside the flower
describe the process leading to fruit formation
1) pollen grain lands on stigma
2) pollen tube grows out of the pollen grain and down through the style to the ovary and into the ovule
3) nucleus from the male gamete moves down the tube to join with a female gamete in the ovule
4) the nuclei fuse to make a zygote which divides by mitosis to form an embryo
5) the fertilised female gamete forms a seed and the ovary develops into a fruit around the seed
how do germinating seeds utilise food reserves
when seeds are underground they cannot photosynthesise so they have a store of food reserves coated in a hard seed coat.
when the seed begins to germinate it uses the glucose from food stores to respire
describe the natural methods of asexual reprosuction
1) runners: fast growing stems that grow sideways, just above the ground.
the runners take root at points in the ground and new plants grow there
describe the artificial methods of asexual reprosuction
cuttings: cutting a bit off the parent plant and planting it
structure of the male reproductive system
1) glands produce liquid to make semen
2) sperm duct carries sperm from testes to urethra
3) testes: produce sperm
4) urethra carries sperm through the penis
5) erectile tissue swells with blood
describe the structure of the female reproductive system
1) ovaries : produce eggs and sex hormones
2) fallopian tubes: muscular tubes that carry ovum from the ovary to the uterus
3) uterus: where the embryo grows
4) uterus lining: good blood supply for the implantation of an embryo
5) cervix
what is the role of the hormones in the menstrual cycle
1) FSH causes an egg to mature and stimulates oestrogen production
2) oestrogen inhibits FSH production and causes the lining of the uterus to thicken
3) LH stimulates the release of an egg
4) progesterone maintains the lining of the uterus and stops LH and FSH production
describe the role of the placenta during pregnancy
lets the blood of the embryo and mother get very close to allow the exchange of food, oxygen and waste.
what is the role of the amniotic fluid
to protect the baby from bumps.
the amnion membrane surrounds the baby and is full of amniotic fluid
what is a genome
the entire DNA of an organism
what is a gene
a section of a molecule of DNA that codes for a specific protein
where are genes located
inside chromosomes in the nucleus
describe a DNA molecule
2 strands coiled to form a double helix
what are the strands of DNA linked by
a series of bases,
adenine + thymine
cytosine + guanine
describe an RNA molecule
single strand; contains uracil instead of T
describe transcription
1) RNA polymerase separates the DNA strands
2) the free RNA nucleotides form complimentary pairs with the bases along the template strand
3) RNA polymerase joins the nucleotides together to produce a sequence of mRNA
4) the mRNA leaves the nucleus and goes to the ribosomes
describe the process of translation
1) the tRNA molecule has an anticodon which is complementary to a specific codon on the mRNA
2) the mRNA molecule enters the ribosome and each codon is matched with an anticodon
3) the ribosome joins the amino acids attached to the tRNA molecules and they form a chain of amino acids (ie a protein)
what is an allele
an alternative form of a gene which give rise to different characteristics
what is codominance
when neither allele is recessive so you show characteristics of both alleles
when does mitosis occur
growth, repair, cloning, asexual reproduction
define a mutation
a rare and random change in genetic material that can be inherited
What is the diploid number of chromosomes in a human
46
What is the haploid number of chromosomes in a human
23
What increases the risk of mutations
exposure to ionising radiation (for example gamma rays, X-rays and ultraviolet rays) and some chemical mutagens (for example chemicals in tobacco
describe the process of evolution by means of natural selection
Variation in a population (due to a mutation)
Limited resources cause competition for survival
Some varieties will have a better chance of survival
They have a better chance of breeding and passing on the allele
Greater proportion of the next generation will have the allele (and the characteristic)
They will outlive those without the allele
why is cloning better than selective breeding
identical / no variation /
all have same characteristic/eq;
2. faster process / quicker process / eq;
4. no need for mating / no need for two parents /
no need to keep bull / no need to keep female /
what is a codon
a sequence of three bases in the gene
how many different possible codons are there
64 (4 different bases and 3 bases in each codon so 4 x 4 x 4)
what do mutations do
change the sequence of DNA bases in a gene, sometimes changing the amino acid and protein it codes for.
what increases risk of mutations
exposure to radiation
chemicals called mutagens
