Genetics Flashcards
what are genes? what are they made of?
They code all the characteristics of an individual.
They are made of DNA.
Where is DNA located in a cell? and in bacteria?
Located in the nucleus of a cell
In the cytoplasm of bacteria as they do not have nucleus.
what are chromosomes?
long threads in the nucleus
how many chromosomes are in each cell in a human?
46 =, 23 from each parent.
what are different versions of the same gene called?
alleles
e.g. eye colour
what is a genotype?
The type of alleles present for a particular gene or genes, e.g. Bb
what is a phenotype?
The way a gene works or expresses itself, e.g. eye colour
what is a dominant gene?
An allele that always expresses itself when if it is present
what is a recessive gene?
An allele which ONLY expresses itself when there is no dominant gene present
what is a homozygous gene?
Both the alleles for a gene are the same e.g. BB bb
what is a heterozygous gene?
Both the alleles for a gene are different
what is codominance?
This happens when both allele are expressed, e.g. pink flowers may be the result of codominance between red and white flowers.
how are genetic diseases caused?
by a faulty allele.
How is cystic fibrosis caused? and What is it?
Caused by a faulty recessive allele involved in making mucus.
The mucus is thick and sticky - increases risk of chest infections. Makes it difficult to create and digest food.
which human blood groups are co dominant?
A and B
which human blood group is recessive?
O
what is polygenic inheritance?
causes a range of phenotypes
How is gender inherited?
Gender is determines by the sex chromosomes.
in humans there are 23 pairs or chromosomes, 22 matching pairs and the sex chromosomes x and y
what is cell division?
cells divide to make new cells which allows growth and repair.
what are the two types of cell division? and what are they for?
Mitosis - growth and repair
Meiosis - making gametes
what does mitosis produce? what are the cells?
Produces genetically identical cells.
Diploid because they contain a full set of chromosomes in pairs.
what occurs in meiosis?
cells divide twice to produce 4 cells.
what is random fertilisation?
The process of fertilisation is random. It depends on which sperm fertilises an egg cell. This causes genetic variation.
what is selective breeding?
Involves humans selecting parent organisms with desired characteristics.
why does selective breeding have to occur over many generations?
It takes years not to inbreed which can result in harmful recessive alleles being passed on to offspring.
how is selective breeding different to natural breeding?
When things are selectively bred a specific outcome is desired, the breeding is monitored while in natural breeding it just happens.
what is genetic variation?
They have different combinations of alleles inherited from their parents.
give an example of a bacteria that is resistant to antibiotics
MRSA
what is a mutation?
a random change to the DNA
what is another name for genetic modification?
Genetic engineering
what does genetic engineering involve?
cutting a gene out of the DNA of one organism and sticking it into the DNA of another organism.
what is a restriction enzyme?
cuts DNA in a specific place
what is transgenic?
an organism containing a gene from another species
what is a vector?
something that transfers the gene
give some examples of vectors
virus
plasmid
what is a ligase enzyme?
sticks pieces of DNA together.
how is genetically modified bacteria grown?
in large fermenters
what is a fermenter?
a larger tank that provides ideal conditions for the growth of bacteria.
what are the ideal conditions for bacteria growth?
warmth
oxygen
glucose
amino acids
why does a fermenter need a water cooled jacket?
to remove excess heat
why does the temperature and pH of a fermenter need to be carefully maintained?
so the enzymes don’t denature because then the bacteria would die.
why is the fermenter sterilised with steam?
- steam will kill all bacteria
- no chemicals in it so no chemical residue which could affect the fermenter
what are the benefits of genetically modified plants?
- solving global hunger, feed more people and can tolerate extreme weather and conditions
- environmentally friendly , resistant to insect and weeds etc so less use of pesticides
- consumer benefits, better flavour + keeping
what is DNA made up of?
a - adenine
t - thymine
c - cytosine
g - guanine
what does a match with
a - t
what does c match with
c - g
how many bases are on a DNA code
3
what is transcription?
gene is copied from DNA to mRNA
when does a mutation occur?
when the base sequence of DNA is changed
what do mutations affect?
the phenotype of an organism
what are the causes of mutations?
ionising radiation
chemical mutagens
what are stem cells?
undifferentiated ( not specialised ) cells that are capable of developing into many different types of cell.
how do cells differentiate (become specialised)
switch some genes on and some genes off.
how many types of stem cell are there?
2
where do embryonic stem cells come from?
come from a 4 or 5 day old embryo
where do adult stem cells come from?
exist throughout the body in different types of tissue
what is therapeutic cloning and why is it used?
- copying the patient’s own stem cells
- their body will not reject a stem cell implant
what are the advantages of stem cells in medicine?
treat a wide range of diseases from cancer to damages tissues
- skin cells for burn victims
- bone marrow cells for blood cancer
- pancreas cells for diabetes
what are the disadvantages of Sten cells in medicine?
- infection
- organ damage
- infertility
- stem cell failure
why do some people believe that using embryonic stem cells is unethical?
the embryo could develop into a human being
what is a clone?
an organism that is genetically identical to another organism
why are transgenic animals cloned?
can be given genes to make human proteins to treat diseases.
