B6 Flashcards
what does DNA stand for?
deoxyribonucleic acid
How many sttrands is DNA made up of? What are they joined by?
2 strands, joined by base pairs
What shape does DNA form?
Double helix shape
Why is DNA a polymer?
Made up of many monomers called nucleotide
What are DNA monomers called? What do they consist of? (3)
Nucleotide, consists of:
- phosphate group (small circles)
- Pentose sugar
- nitrogen containing group
What does each chromosome contain?
Different genes
What does a bigger chromosome mean?
Longer DNA
What chromosome determines your gender?
Sex chromosomes, the 23rd pair
What chromosomes do females/ males have?
Females - XX
Males - XY
What is a gene? (3)
A small section of DNA that code for a particular protein
- codes for a sequence of amino acids
- it is a small segment of a chromosome
What do genes do?
Code for a sequence of amino acids
- when these amino acids are combined in this sequence they form a protein
How many types of amino acids are there?
20
- can be combined in so many combinations, so can make thousands of proteins
What does DNA determine? ( In terms of proteins)
Which protein a cell produces, e.g red blood cell needs lots of the protein haemoglobin
What is a genome?
The entire set of genetic material to an organism
- your genome will be similar to your parents and identical to your twin’s
What do genomes allow us to identify?
Genes that cause disease
- certain genes increase the risk of disease
What are the steps for meiosis?
What are ④ similarities of mitosis and meiosis?
- Both produce new cells
- involves copying of chromosomes
- involves copying of cell organelles
- Both involve new membranes forming
What are 4 differences of mitosis and meiosis.
- mitosis produces cells identical to the parent cells
Meiosis produces cells that are unique - cells produced by mitosis contain the same number of chromosomes as original cell
Cells produced by meiosis have half the number of chromosomes - Mitosis takes place in body cells
Meiosis takes place in reproductive organs - Mitosis is for growth and repair
Meiosis is only for making gametes
What is sexual reproduction?
Reproduction involving gametes
How are gametes produced?
By meiosis
What is meant by dominant allele?
The version of the gene that will display
What does heterozygous mean?
2 alleles for a characteristic are different.
What is a phenotype?
The physical expression of a pair of alleles
What are alleles?
A different version of the same gene
What are the 2 causes of variation within a species?
Genetics and the environment.
What can be used to study extinct animals?
Fossils
What are 3 main ways fossils are formed? Explain in depth
- Gradual replacement by minerals
- body parts such as teeth, bones and shells decay really slowly → meaning they can be replaced with minerals whilst decaying and form rock like substances which are in the exact same shape and size as the original structures → when dug up and separated from rock, we are left with perfect the model. - Casts and impressions (similar types of fossils)
- casts → organisms are buried in soft material (e.g clay), as clay hardens the organism decays → left with a gap that is the same size and shape as the organism
- impressions → when organisms leave a mark on the ground that stays there for time ( e. g footprints ) - Fossils can be formed by preservation when no decay happens at all.)
- when organisms get stuck in amber or tar pits → because there is no oxygen on moisture, no decay can take place so organism remains completely intact
- also happens in glaciers where it is too cold for microorganisms that normally carry out the decay process to survive or in peat bogs where it is too acidic for microorganisms.
Why are there periods in time where we don’t know what happened?
l. Many early life forms where soft bodied so would have decayed quickly making any fossil remains unlikely
- Fossils formed long ago where destroyed by earthquakes and volcanos.
What are 3 reasons for extinction?
- Environment changes too quickly ( e.g. Too hot /too cold)
- New predators, including humans.
- New diseases → kills them all
What is cystic fibrosis cause?
A homozygous recessive (ff) genetic disorder Results in the body producing a lot of thick sticky mucus in the air passage and in the pancreas.
What are 3 symptoms of cystic fibrosis?
- chest infection
- Low energy levels
- Sticky mucus
What is polydactyly
A dominant genetic disorder that causes babies to be born with extra fingers/ toes.
Explain the steps for genetic screening (5)
- Mother is given hormone (fsh and lh) to stimulate many eggs to be produced
- Eggs are collected and fertiliseel using sperm from father.
- Fertilis ed eggs are allowed to develop into embryo is and one cue from each embryo is removed.
- These alls are tested for the allele linked with the disorder
- Embryos which do not have the allele allele are implanted into the mother’s womb, other embryos may be destroyed
What are 2 advantages of genetic screening?
- Babies would be born tree of the disorder screened for
- Avoids costs of large long -term treatment
What are 3 disadvantages of genetic screening?
- many more embryos than needed are erected → which means they will usually be destroyed
- Some disorders are not life shortening
- Could lead to negative perceptions and feelings about disability.
What are 3 economic issues / benefits with genetic screening?
- Cost of screening
- Raising child with disorder
- Lower medical bills
What are 2 social issues / benefits with genetic screening?
- Healthy sibling may feel neglected or have to help look after sibling
- Parent lifestyle.
