Reproduction (Inheritance, Variation and Evolution pt1) Flashcards
What does Asexual reproduction involve?
- one parent
- no fusion of gametes ( no mixing of genetic information)
- the production of genetically identical offspring
- mitosis
What are examples of asexual reproduction?
- Strawberry plants send out runners which touch the ground and grow a new plant
- daffodils produce lots of smaller bulbs that can grow into new pants
- many fungi reproduce asexually by spores
- Malarial protists reproduce asexually when they are in the human host
What does sexual production involve?
- the fusion of male and female gametes: sperm and egg; pollen and egg
- the mixing of genetic information leads to variation in offspring
- formation of gametes involves meiosis
How is meiosis carried out?
1) Before the cell starts to divide, it duplicates its genetic information forming to armed chromosomes
2) Chromosomes pairs line up in the centre of the cell
3) Chromosomes part company and move to opposite poles
4) cell divides for the first time
5) Chromosomes line up again in the centre of the cell and the arms of the chromosomes are pulled apart
6) 4 haploid cells are formed, each half the number of chromosomes of the parent cell
all gametes are genetically different from each other
How are the 23 pairs of chromosomes restored after meiosis and what happens after this process
in sexual reproduction, 2 gametes, one from male and one from female, join together to restore the full number of chromosomes = fertilisation
new cells divide by mitosis = embryo
cells become specialised by differentiated
What are the advantages of sexual reproduction?
- produces variation in offspring
- if the environment changes, variation gives a survival advantage by natural selection
- natural selection can be speeded up by humans in selective breeding to increase food production
What are the advantages of asexual reproduction?
- only one pared is needed
- more time and energy-efficient as they don’t need to find a mate
- faster than sexual reproduction
- many identical offspring can be produced when conditions are favourable
What are examples of times when organisms using both asexual reproduction and sexual reproduction depending on the circumstance?
- many fungi reproduce asexually by spores but reproduce sexually to give variation
- malaria parasites reproduce asexually in the human host, but sexually in the mosquito
- many plants produce seeds sexually but also reproduce asexually by runners such as strawberry plants, or bulb division such as daffodils
What is the genome of an organism?
the entire genetic material of that organism
What is a gene?
- a small section of DNA on a chromosome, which codes for a particular sequence of amino acids, to make a specific protein
The whole human genome has now been studied.
What does this enable us to do?
- doctors can search for genes linked to different types of disorders
- helps scientists understand the cause of inherited disorders ad how to treat them
- we can use the human genome to trace human migration patterns from the past and how humans may have changed over time
Ho many different repeating nucleotides is DNA made from?
4
What do nucleotides consist of?
common sugar, phosphate and one of the 4 bases
AGCT
What do the order of bases do?
it controls the order in which amino acids are associated to produce a particular protein
which bases are attracted to each other
C=G
A= T
How are proteins made?
1) proteins are synthesised on ribosomes, which is in the cytoplasm. During transcription, mRNA is used as a template to copy the base sequence of the gene in the nucleus
* mRNA is a single strand molecule
2) mRNA then passes out of the nucleus to the cytoplasm
3) Translation: mRNA molecule attaches to a ribosome.
4) carrier molecules (aka tRNA) then bring specific amino acids to add to the growing protein chain in the correct order
5) when the protein chain is finished, it folds up to form a unique shape
* this unique shape allows the proteins to do their job as enzymes, hormones or structural proteins such as collagen
What is a mutation?
a random change in DNA structure
Why are most mutations harmless?
because they don’t alter protein, or only alter it slightly so that its appearance or function is not changed
What increases the rate of mutations?
- certain chemicals and high-energy radiation
What happens if any base in the DNA is changed?
it may change the order of amino acids in the protein coded for by the gene
What could happen when A few mutations code for an altered protein with a different shape.
An enzyme may no longer fit the substrate binding site
a structural protein may lose its strength.
What happens if there is a mutation in the non-coding parts of DNA
it may affect how the genes are expressed
What is an allele
an alternate form of a particular gene
What is a phenotype?
How the alleles are expressed
What does homozygous mean?
when two alleles are the same
What does heterozygous?
alleles are different
What are most characteristics the result of?
what is it called when only one gene is involved?
multiple genes interacting, rather than a single one
monohybrid inheritance
What type of allele is Polydactyly (extra fingers or toes)?
dominant
What type of allele is Cystic fibrosis?
recessive allele
What is embryo screening?
During IVF, before embryo is implanted into the mother’s womb, a cell is removed from each embryo an is analysed for its genes
Embryos do not that have defective alleles are implanted into the women
What are the positives of embryo screening?
- screening will stop people from suffering
- treating disorders cost the government a lot of money
- there are laws to stop it from going too far
What are the cons of embryo screening?
- screening is expensive
- unethical = many embryos are destroyed
- some people may want to produce an embryo with desirable feature - unethical
what are the chromosomes for female and male
female = XX
Male = XY
