inheritance, variation and genetics - b6 Flashcards
what is the structure of dna
a double helix structure with two strands
what is a chromosome
a tightly coiled piece of dna
how many chromosomes does a cell have
46, 23 pairs
what is a gene
a section of the dna that codes for specific protein
what is the genome
the entire genetic material in an organism
what are the benefits of knowing the entire genetic material
we can know what genes cause diseases and trace the paths of our ancestors
what is an allele
the different versions of a particular gene
what does a homozygous allele mean
both alleles from both parents are the same
what does a heterozygous allele mean
both alleles are different
what is a genotype
the two alleles someone has for a gene
what is a phenotype
the characteristics expressed by a genotype
what is the structure of dna
a sugar phosphate backbone with bases attached
why is dna considered a polymer
because it is made up of the same monomers called nucleotides
what is trasncription
copying a single gene of dna into mrna
what is special bout mrna compared to dna
its shorter and its only a single strand
what is translation
the formation of a sequence of amino acids from a triplet code
what is a chain of amino acids called
a polypeptide
what is a mutation?
a change to the base codes of dna
what usually increases the risk or a mutation
carcinogens and ionising radiation
what are the three types of mutation
substitution, insertion and deletion
what is a substitution mutation
when a particular base on the dna is replaced
what is a insertion mutation
when a base is added to a gene
what is deletion mutation ?
when a base is deleted from a gene
where do mutations ususally occur
in the non-coding part of the dna
what is sexual reproduction
when a male gamete and a female gamete fuse = fertilisation
what does sexual reproduction produce
genetically different offspring
how many chromosomes to human gametes have and what cause this
23 - meiosis
what is asexual reproduction
when only one parent is involved and the offspring are gentically identical
what the pros of asexual reproduction
its quicker as it only involves one parent
- so a species can populate an entire area quickly
what are the cons of asexual reproduction
there is no genetic variation so a disease could quickly wipe out a whole population
they would struggle to adapt to changing environment
what are the pros of sexual reproduction
there is genetic variation so a disease will not wipe out a whole population
they can adapt to changing environments and evolve
what are the cons of sexual reproduction
it is time consuming as a lot of time and energy has to go into finding a mate
the characteristics they have are most likely for attraction and not survival
is cystic fibrosis an recessive or dominant condition
recessive
what is cystic fibrosis
a condition that causes thick, sticky mucus to build up in the lungs and the digestive system
what is polydactyly
a condition that causes someone to be born with extra fingers or toes
is polydactyly causes by a recessive or dominant allele
dominant
what is embryo screening
looking at the cells of an embryo (usually during IVF) to check for any genetic disorders
if there is a genetic diorder they might decide to disregard the embryo
what are the pros of embryo screening
it reduces the total amount of suffering
saves money
what are the cons of embryo screening
its unethical because you are throwing away a life that could have been a human
it also presents the idea that people with genetic disorders are less desirable
who was gregor mendel
a scientist that discovered the laws of inheritance
what plants did he use and what did he measure
pea plants
measured colour of pods, height and colour of flowers
what did he find about inheritance
he found that different characteristics were being expressed in different generations
he called this hereditary units and they could be dominant or recessive
what is natural selection
when the organisms with the most favourable qualities survive in an environment
what is evolution
when the inherited characteristics of a species change over time due to natural selection
what influences variation
genes and environment
what cause genes to change
mutations
what was lamarcks theory of evolution
that the characteristics an organism gained during its lifetime changed its dna and these traits were passed onto its offspring
what was darwin’s and wallaces’s theory of evolution
organisms within a species were varied
the ones with the most desirable characteristics survived and passed these down to their offspring
this keeps happening until the whole species has evolved to have them all have that one desirable trait
what is selective breeding
it is when the organisms with the best traits are chosen out of a population and bred together to create offspring that has even better traits
what are the cons of selective breeding
it decreases variation and the gene pool
this means the whole population is at risk of getting a disease
also as the organisms that are bred are closely related they are more likely to get inbreeding = more rare birth defects and diseases
what is genetic engineering
modifying an organism by taking the desirable trait from one organism and putting it in it
give examples of things that have genetically modified
sheeps milk - contains drugs that can treat diseases
bacterial plasmids- given them the gene for insulin so when they divide they produce more and we can harvest it
rice- golden rice contains beta carotene which protects people from going blind
what is gene therapy
treating an inherited disorder by giving somone a healthy copy of faulty gene
what are the cons to gene therapy
it would be hard as the new gene would have to be put in every cell
to solve do it at an earlier stage of development
what are the pros of gm crops
better yield = more food for cheaper
better taste
resistance to diseases
what are the cons of gm crops
we dont know the full side effects of them, they could end up harming us
also there is a chance they could end up in the wild, overtake other plants and change a whole ecosystem
how do we genetically engineer
first take the desired gene and isolate it from the dna
then put it in a vector like a virus or bacterial plasmids
these can then go into a human, the body cells will absorb the vector and start to produce that gene in dna replication
how can we clone an animal
- take an egg cell from a donor mum and take the nucleus out so its enucleated
- take an adult skin cell from the animal you want clone, remove its nucleus and put the nucleus from the egg cell inside
- stimulate the egg with a small electric shock so that it multiplies to form an embryo4. place in a surrogate mum and the embryo will develop normally to create a foetus.
what is a trasngenic organism
an organism that has dna from another species
what are the pros of trangenic organisms
we can give them the gene to code for helpful proteins and then use it for what we need
how do you clone from embryonic transplant
1.take a male and female with desirable traits and fuse their egg and sperm cell together
2. let the new zygote multiply into an embryo
3. separate each embryo cell from each other
4. put each one in 1 surrogate mother
5. the embryo will develop normally and all the offspring will be identical
what are fossils
the remains of animals from millions of years ago that are found in rocks
what are the ways that fossils are formes
- gradual replacement by minerals , things like bones and shells take longer to decay and as they do they are replaced my minerals leaving a rock in the same shape as them
- cast and impressions , if animals are buried in soft materials, as they decay and it hardens they leave an imprint or impressions like a footprint
-preservations - when they are preserved in a place that does not have the write conditions for decay like amber, tar pits, ice and peat bogs
why is the fossil record not complete
-some organisms that lived earlier were very soft bodied and so decayed very quickly
-fossils from before have been destroyed
why do species go extinct
-natural disasters
-disease
new predators
-more competition
-catastrophic event
-loss of habitat
rapid change in temperature
