Variation and Inheritance Flashcards
1
Q
What does heterozygous mean?
A
- if the two alleles for a particular gene are different
2
Q
What type of allele is polydactyly caused by?
A
- a dominant allele
3
Q
How are embryos screen for alleles that cause disorders?
A
- DNA is isolated from the embryo’s cells
- a gene probe is produced that will bind to the allele for a specific disorder
- the probe is also labelled so that it can be detected. it is usually a fluorescent chemical that can be seen when UV light is shone
- the probe is added to a mixture containing the DNA sample from the embryo. if the embryo’s DNA contains the allele for the disorder. the probe will bind to it
- UV light is then shone onto the sample, if it has the disorder, it will be glowing
4
Q
What are the pros of GM crops?
A
- GM crops can increase the yield of a crop, making more food
- GM crops may help developing nations who lack nutrients. e.g. golden rice
- GM crops are being grown outside of UK with no problems
5
Q
What are the cons of GM crops?
A
- it will affect the number of weeds and flowers, and so the population of insects. reduces farmland biodiversity
- they may not be safe, or people may develop allergies
- transplanted genes may get out into the natural environment, e.g. herbicide resistance gene may create a superweed
6
Q
What shape is DNA and what is the structure?
A
- shape of a double helix
- two strands are held together by chemicals called bases
- the order of bases decides the order of amino acids in a protein
7
Q
What are the pros of cloning?
A
- ideal offspring
- lead to a greater understanding of the development of embryo, ageing and age-related disorders
- help preserve endangered species
8
Q
Why do organisms of the same species have differences?
A
- genetic variation
- environmental variation
- both
9
Q
What is asexual reproduction?
A
- no fusion of gametes and only one individual is needed as the parent.
- there is no mixing of genetic information and so no genetic variation in the offspring.
- these genetically identical individuals are known as clones
10
Q
What is a dominant allele?
A
- an allele that controls the development of a characteristic when it is present on only one of the chromosomes
11
Q
How can plants be cloned?
A
- by tissue culture: a few plant cells are put in a growth medium with hormones and they grow into new plants, clones of the parent plant
- these plants can be made very quickly, in very little space and be grown all year
12
Q
How many pairs of chromosomes are there in every human body cell?
A
- 23 pairs
13
Q
What are the arguments for embryonic screening?
A
- it will help to stop people suffering
- treating disorders cost the Government and taxpayers a lot of money
- there are laws to stop it going too far. parents can’t even choose the sex of their baby
14
Q
What is a recessive allele?
A
- an allele that controls the development of a characteristic one if the dominant allele is not present
15
Q
What are the arguments against embryonic screening?
A
- it implies that people with genetic problems are undesirable, leading to prejudice
- in the future, maybe everyone will want to screen embryos for a desirable baby
- screening is expensive
- for embryos in the womb, it could lead to termination
- screening is not 100% accurate
- taking cells from embryos in the womb increase the chance of a miscarriage
16
Q
What is DNA?
A
- stands for deoxyribonucleic acid
- contains coded information
- found in the nucleus of animal and plant cells in really long molecules called chromosomes
17
Q
How can you use embryo transplants to make animal clones?
A
- sperm cells taken from a prize bull and egg cells from a prize cow
- the sperm are then used to artificially fertilise an egg cell.
- the embryo that develops is then spit many times before any cells become specialised
- these cloned embryos can then be implanted into lots of other cows where they grow into baby calves, genetically identical
18
Q
What does homozygous mean?
A
- if an organism has two alleles for a particular gene that are the same
19
Q
What is a gene?
A
- a gene is a section of DNA
- each gene codes for a particular combination of amino acids which are put together to make a specific protein
20
Q
What are alleles?
A
- Different forms of the same gene
21
Q
What are the cons of cloning?
A
- you get a reduced gene pool, meaning there are fewer different alleles in the population. a disease could wipe out everything, as there is no allele giving resistance
- cloned animals might not be as healthy
- humans may be clones in the future, unsuccessful attempts may mean there are severely disable children born
22
Q
What are GM crops?
A
- genetically modified crops are crop plants that have had their genes modified e.g. to make them resistant to viruses, insect attacks or herbicides
23
Q
What is adult cell cloning?
A
- taking an unfertilised egg cell and removing its genetic material (the nucleus)
- a complete set of chromosomes from an adult body cell (e.g. skin cell) is inserted into the empty egg cell
- the egg cell is then stimulated by an electric shock, making it divide like a normal embryo
- when the embryo is a ball of cells, it is implanted into an adult female, to grow into a genetically identical copy of an original adult body cell
24
Q
What is Down’s Syndrome caused by?
A
- inheritance of an extra chromosome
- 47 instead of 46
25
What is genetic engineering?
- a useful gene is cut from one organism's chromosome using enzymes
- this gene is inserted into a vector, usually a virus or a bacterial plasmid
- the vector is then used to insert the gene into a different organism, or into the chromosome of the different organism. the DNA is used to make a protein
26
What type of sickle cell anaemia is polydactyly caused by?
- a recessive allele
| - less likely to get malaria if you carry the sickle-cell allele (heterozygous Aa)
27
What type of allele is cystic fibrosis caused by?
- a recessive allele
28
What is sexual reproduction?
- the joining (fusion) of male and female gametes. the mixture of the genetic information from two parents leads to variety in the offspring
