inheritance Flashcards
where might you find 23 pairs of chromosomes and what are the exceptions
nucleus of human cells
gametes - sperm and egg cells have 23 single chromosomes
what is sexual reproduction, what process does it involve, and what will offspring look like
- involves the fusion if male and female gametes (fertilisation)
- meiosis
- genetic information is mixed, variation in offspring
what is asexual reproduction,what process foes it involve, and what will offspring look like
- only one parent
- mitosis
- no fusion of gametes, no mixing of genetic information - clones (genetically identical offspring)
where does meiosis occur
reproductive organs (ovary/testes)
purpose of meiosis and how does it work
where one cell produces 4 gametes with half the number of chromosomes
- all chromosome pairs are copied
- cell divides into 2, one pair each
- cell divides again, single chromosomes
what happens after meiosis in sexual reproduction
- gametes fuse (fertilisation), cell has normal number of chromosomes
- cell divides (mitosis), clump of identical cells (embryo) formed
- cells differentiate and embryo develops e.g nerve/muscle cells
advantages of sexual reproduction
- variation: increased survival of change in environment
- these individuals breed and pass survival genes on - natural selection
what is selective breeding
where individuals with survival genes are bred
- increases food quality and yield
advantage if asexual reproduction
- only one parent/no mate: faster as less energy and time needed
- fast: extremely useful in favourable conditions, offspring produced rapidly
disadvantage of asexual reproduction
- no variation: could all die in unfavourable conditions
what organisms can reproduce by both methods
malaria
fungi
plants
how do malarial parasites reproduce
life in mosquito vector: sexually
life in human host: asexually
how does fungi reproduce
spores (become new fungi) can be produces asexually and sexually
how can plants reproduce
- sexually to produce seeds
- asexually e.g
• strawberry plants grow runners which form new plants when they hit soil
• bulb division: bulb produces buds, becomes offspring
what is dna
genetic material found in chromosomes
structure of dna
two strands, polymers (made up of nucleotides) twisted in double helix
what is a gene
small section of dna on a chromosome that each codes for a particular sequence of amino acids to make a specific protein
what is a genome
entire set of genetic material in an organism
advantages of understanding human genome
- identify genes linked to diseases e.g Alzheimer’s
- understand and treat inherited disease e.g cystic fibrosis
- trace past human migration patterns to discover ancestry
what determines a protein
sequence order of amino acids determines shape, which determines function
structure of nucleotide
phosphate group attached to sugar molecule, always the same
sugar is attached to one of four bases, a, c, g, t, which pair complimentarily: A links with T, C links with G
what determines the order of amino acids in a protein
sequence of bases in the gene for that protein
the cell reads the bases as triplets (e.g ATG), each triplet codes for a specific amino acid in the protein
what and where is first stage of protein synthesis
transcription: nucleus
sequence of bases of gene is copied into a complementary, single strand, template molecule: mRNA
this passes out of nucleus and into cytoplasm
what and where is second stage of protein synthesis
translation: cytoplasm
- mRNA attaches to a ribosome
- carrier molecules (tRNA) bring amino acids to ribosome
- ribosome reads triplets of bases on the mRNA to join correct amino acids in correct order
- complete protein chain folds into its unique shape
what is a mutation
a random change to a base of dna.
most of the time, change will not change the sequence of amino acids, so will not effect shape or function of protein
if it changes the sequence, shape and function of protein
what can a mutation in dna that codes for proteins lead to
most of the time, change will not change the sequence of amino acids, so will not effect shape or function of protein
if it changes the sequence, shape and function of protein can change:
- active site of enzymes, no longer bind to stubstrate
- strength of structural proteins, e.g collagen loses strength and becomes useless
what do non-coding dna regions do
tell genes when to produce proteins
what can a mutation in a region of non-coding lead to
effects how genes produce proteins and dont produce proteins
e.g protein produced when it shouldnt have been & cell is not meant to have
significant effects e.g uncontrolled mitosis which leads to cancer
