B1 - You and Your Genes

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Cambridge IGCSE Biology Flashcards on B1 - You and Your Genes, created by franimal on 10/10/2013.

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Created by franimal about 6 years ago
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Question Answer
What are the two factors that affect someone's appearance? Give an example! Inherited - eye colour, skin colour, etc. Environment - tattoos, scars, etc. Weight, height etc are all combinations!
Put these in size order, largest to smallest: nucleus, chromosome, cell, gene Cell Nucleus Chromosome Gene
What are genes? A gene is an instruction for making one specific protein.
What is a structural protein? A protein for building the body, eg collagen, the protein found in tendons.
What is a functional protein? A protein that takes part in the chemical reactions of the body, eg amylase is an enzyme.
What are clones? Do they occur in Nature? A clone is an organism genetically identical to another organism. Identical twins, strawberry plants and many others are clones.
What is an inherited disorder? A disorder passed down from parents to children through their genes.
How many (non paired) chromosomes in a normal cell, a sex cell and a fertilised egg? Normal - 46. Sex cell - 23 and 23. Fertilised - 46.
What gene causes the male's testes to develop in a 6-week-old embryo? The SRY gene. 'sex-determining region of the Y chromosome'
What are hormones? Hormones are chemicals that control many processes in the cells. Tiny amounts of hormones are made by different parts of the body.
Chromosomes come in pairs. Do the chromosomes in each pair have the same sets of genes or not? The same. The chromosomes may contain different versions of the same gene, but the two 'match', one from either parent.
What are alleles? Different versions of the same gene.
What is your genotype and your phenotype? Genotype - the inherited alleles Phenotype - your characteristics, eg eye colour
The D allele is dominant. What does this mean? You only need one copy of a dominant allele to have its feature.
What is a Punnett square? A genetic diagram that shows all the possibilities for one couple.
The d allele is recessive. What does this mean? You must have two copies of a recessive allele to have its feature, one from each parent.
If you inherit both alleles exactly the same, what are you for that characteristic? homozygous
If you inherit different alleles, what are you for that characteristic? heterozygous
Some disorders are single gene disorders. What does this mean? The feature is dominant - a H instead of an h. You only need to inherit it from one parent.
What is cystic fibrosis? A recessive genetic disorder that causes mucus to be much thicker than it should be.
Jim has the alleles Ff. What does this make him when a disease is recessive? A carrier of the disease. He won't experience any symptoms but if he has a child with another carrier, that child could be clean, a carrier too or a patient.
There are two tests that can take place during a pregnancy to see whether a child has a genetic disorder. What are they, without descriptions? The chorionic villus test. An amniocentesis test.
Describe an amniocentesis test? Include miscarriage risk and when the results can be taken. Amniotic fluid is withdrawn from the womb using a needle. 1% miscarriage risk with results at 15-18 weeks.
Describe a chorionic villus test? Include miscarriage risk and when the results can be taken. A suction tube inserted up the vagina removes cells from the placenta. 2% miscarriage risk with results at 10-12 weeks.
What is an ethical question? When a person has to make a decision on the right or wrong way to behave.
Give an example of an ethical question (that relates to this subject). Whether to terminate a pregnancy. Whether to use embryonic stem cells.
Why might someone believe terminating a pregnancy is wrong? All life is sacred. We shouldn't pick and choose our children. We have a duty to protect children. The way a child is, even if disabled, is God's will.
Why might someone believe terminating a child is okay? Up until 22 weeks, the baby is just a mass of cells. It's the parents choice. It's the woman's body. Having a baby that will suffer in life is wrong. Having an ill child is expensive to the NHS.
What's a false negative and a false positive? When a test comes back either positive or negative but the result is faulty. Fairly rare.
What is genetic screening? Testing a population for a particular allele, eg the Jewish community screened all those engaged for Tay-Sachs
How can genetic testing be used to find the correct treatments? Some people react very badly to some drugs, because of their genes. How responsive you are could be tested genetically.
What are the 3 reasons someone may want to be genetically tested? 1. So they can plan their life, if they will develop the disease. 2. If they're a carrier and are worried for future children they might have. 3. If they're at greater risk of heart disease etc they may alter their lifestyle.
Why shouldn't insurance company's know the results of genetic tests? After 2014 they could use them to charge higher premiums or not give life insurance to those who will probably die early.
How do the police use genetic information? DNA is collected from crime scenes and can be matched to criminals in a national database.
What is PGD? Pre-implantation genetic diagnosis, similar to IVF but at the 8-cell stage the embryo is tested for disorders.
Why would people be against PGD? It's considered 'playing God' with genes and they worry that it will lead to designer babies. 'Faulty' embryos are often destroyed.
Why would people be pro PGD? It insures no babies are born with genetic disorders and removes the need to terminate a pregnancy.
What is asexual reproduction? When an organism reproduces by dividing, causing children that are clones of the adult.
What are stem cells? Unspecialised cells that can grow into more cells.
Why do some people want to clone human cells within embryos? Embryonic stem cells can be rejected by the body as in a transplant, unless the DNA is the same as in the adult.
Why are embryonic stem cells more useful than adult ones? Embryonic stem cells can turn into any part of the body, but adult stem cells are very limited.