Reproduction and inheritance Flashcards
Where and what are chromosomes?
- found in the nucleus
- they are long lengths of DNA coiled up
- they contain your genetic material
What is a gene?
- a short section of DNA
- each separate gene is a chemical instruction that codes for a particular protein
What are human body cells and how many chromosomes are there in total in a nucleus?
- diploid=2 copies of each chromosome
- 46 chromosomes in total in a human cell
What are the role of proteins in inheritance?
-control most processes in the body and determine inherited characteristics e.g eye colour
What are alleles?
-different versions of the same gene
What is asexual reproduction?
- only one parent
- the offspring have identical genes to the parent
How does asexual reproduction work?
-Mitosis, an ordinary cell can make a new cell which is genetically identical by dividing in 2
Examples of organisms which reproduce asexually.
- bacteria
- some plants
Define mitosis.
-when a cell reproduces itself by splitting to form 2 cells with identical sets of chromosomes
Explain the steps of mitosis.
- in a cell thats not dividing, the DNA is spread out in long strings
- it duplicates its DNA forming X shaped chromosomes
- the chromosomes line up in the centre of the cell and cell fibres pull them apart
- membranes form around each of the sets of chromosomes which become the nuclei of the 2 new cells
- the cytoplasm divides
Define sexual reproduction.
- where genetic info from 2 organisms is combined to produce offspring which are genetically different to either parent
- the mother and father produces gametes (egg cell and sperm)
What are gametes in terms of no. of chromosomes?
- haploid= half the no of chromosomes in a normal cell
- 23
Fertilisation…
- a male gamete fuses with a female gamete to form a zygote which ends up with a full set of chromosomes
- the zygote undergoes cell division by mitosis and develops into an embryo
- the embryo inherits features from both parents
What is meiosis?
- a type of cell division
- produces four haploid cells
- only happens in the reproductive organs
Steps of meiosis.. (first division)
- duplicates its DNA
- the chromosomes line up in pairs in the centre of the cell, one chromosome in each pair came from mother and one from father
- the pairs are pulled apart = each new cell has one copy of each chromosome
- each new cell has a mixture of mother and fathers chromosomes
Steps of meiosis.. (second division)
- the chromosomes line up again in centre of cell, the arms of the chromosomes are pulled apart
- you get four haploid gametes which have a single set of chromosomes
What is the female reproductive part in plants?
-the Carpel
What does the carpel consist of?
- ovary, stigma and the style
- stigma=end bit that pollen grains attach to
- style=rod like section that supports the stigma
- ovary=contains female gametes inside ovules
What is the male reproductive part in plants?
-the Stamen
What does the Stamen consist of?
- anther and the filament
- anther=contains pollen grains which produce male gametes
- filament= stalk that supports the anther
What is pollination?
-transfer of pollen from an anther to a stigma so the male gametes cam fertilise the female gametes
What is cross pollination?
- type of sexual reproduction where pollen is transferred from the anther of one plant to the stigma of another
- plants that cross pollinate rely on insects or wind
How are some plants adapted for insect pollination?
- brightly coloured petals to attract insects
- scented flowers and nectaries to attract insects
- they make big sticky pollen grains which stick to insects as they go from plant to plant
- the stigma is sticky so pollen picked up by insects will stick to it
How are some plants adapted for wind pollination?
- small dull petals on the flower
- no nectaries
- a lot of pollen grains- theyre small and light=carried by wind
- long filaments that hang the anthers outside the flower=lots of pollen gets blown away
- large, feathery stigma to catch pollen as its carried past the wind
Steps of fertilisation in plants…
- pollen grain lands on stigma of a flower
- a pollen tube grows out of the pollen grain and down through the style to the ovary and into the ovule
- the two nuclei fuse together to make an zygote. Divides by mitosis to make an embryo
- each fertilised female gamete forms a seed, the ovary develops into a fruit around the seed
What are the roles of runners?
- plants can reproduce asexually using runners
- the parent plant sends out runners-fast growing stems that grow out sideways, just above the ground
- the runners take root at various points and new plants start to grow
- the new plants are clones of the parent plant so there is no genetic variation
What are the roles of cuttings?
- artificial method to clone plants
- garderners can take cuttings from good parent plants and then plant them to produce genetically identical copies of the parent plant
- these plants can be produced quickly and cheaply
Define homozygous.
-you have 2 alleles the same for that particular gene e.g CC or cc
Define heterozygous
-you have 2 different alleles fo that particular gene e.g Cc
Environmental factors of genetic variation in humans.
- health
- sporting ability
Environmental factors of genetic variation in plants
- sunlight
- temp
- mineral content
