B1 - You and your Genes

Topic also includes 'Reproduction and variation'.

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Where are the instructions which control how an organism develops and functions found. What are they called?
These instructions, called genes, are found in every cells nucleus.
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What do genes carry?
Instructions for making protiens.
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What are the two different types of protien called?
Protiens can be structural (for example; collagen) or functional (for example; enzymes like amylase).
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What are genes made of and where are they found in the nucleus?
Genes are made up of long sections of DNA and they are found in chromosomes.
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Describe the difference between genetic and enviromental characteristics.
Genetic factors, such as dimples, are present from birth and are caused by our DNA. Environmentall factors, such as scars, are a product of our surroundings. Some characteristics, such as weight are affected by genetics and the environment.
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Many characteristics are caused by...
...several genes working together.
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How many chromosomes does a nucleus contain? How many chromosomes does a gamete contain?
Human cells contain 46 chromosomes (23 pairs) in their nucleus. Gametes contain 23 chromosome - one from each pair.
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What are alleles?
Chromosomes carry the same genes in the same places however there may be different versions of the gene; called alleles.
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How many alleles for each gene does a person usually have?
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What do homozygous and hetrozygous mean?
Homozygous refers to when a person has the same allele for a particular gene. Hetrozygous refers to when a person has different alleles for a particular gene.
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How is variation produced in offspring?
Genes from both parents are used in sexual reproduction to produce variation.
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Why do offspring have similarities with both of their parents?
The combination of maternal and paternal alleles in a fetilised egg makes sure that the offspring has some characteristics in common with both parents.
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Why are two (or more) offspring from the same parents genetically different?
Differrent offspring inherit different combinations of maternal and paternal alleles.
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What are dominant and recessive alleles?
Dominant alleles will show their associated characteristic even if there is only one in a pair. Recessive allels will only show if both alleles are resessive.
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Which sex chromosomes do males have? Which do females have?
Male: XY / Female: **
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What causes testes to develop? What cause ovaries to develop?
The sex-determining gene (SRY) on the Y chromosome cause testes to develop. The absence of the SRY gene will cause ovaries to develop.
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Explain what a punnet square is.
Punnet squares are diagrams which show how dominant and recessive/sex chromosmes are inherited.
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What do the terms 'genotype' and 'phenotype' mean?
Genotype = the genetic make up of an organism (combination of alleles) / Phenotype = Observable characteristics of an organism (physical appearence).
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What causes disorders such as Cystic Fibrosis and Huntingtons disease?
Faulty alleles on a single gene.
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Is Huntington's caused by a dominant or recessive alleles? Is cystic fibrosis caused by a dominant or recessive allele?
Huntington's is caused by a dominant allele whereas Cystic Fibrosis is caused by a recessive allele.
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What are the symptoms of Huntington's and cystic fibrosis?
Huntingtons: late onset, tremor, clumsiness, memory loss, inability to concentrate and mood changes / Cystic Fibrosis =thick mucus, difficulty breathing, chest infections, difficulty in digesting food.
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What is a carrier (of genetic disease)?
Someone with one allele of a recessive genetic disorder who shows no symptoms of the disease put may pass the disease on if they have children with anotherr carrier of the same disorder.
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Explain how punnet square show how a recessive single gene disorders are inherited.
A punnet square with different combinations of alleles can be used to calculate the risk of a child having or being a carrier of a genetic disorder.
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Describe when genetic screening for embryos, children and adults is used.
Embryo: Pre-Implamentation-Diagnosis for chosing which embryos to implant (Fertility treatment) / Children: Predictive testing for genetic diseases. / Adults: Testing individuals before prescribing drugs.
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What implications do testing adults and fetuses for alleles carrying genetic disease have?
1) Risk of miscarrage as a result of cell sampling fot the test. 2) False positive and false negatives have an impact on decissions e.g abortion, informing family and family planning.
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What implications does pre-implemntation genetic testing have.
This sort of testing could lead to 'designer babies' where parents select athsetic characteristics or even sex to fit there preference. Some results could lead to termination of a pregnancy.
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What are the implications of employers and insurance companies genetically screening applicants.
Aplicants may be turned down by employers and insurance companies on the grounds of their genetics which is something they have no control over.
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How are clones made naturally?
Bacteria, plants and some animals reproduce asexually to produce offspring genetically identical to eachother and to their parent. Twins are another example of natural clones.
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How do differences between clones occur?
Differences betweeen clones are due only to environmental factors.
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When do clones of plants occur naturally?
When plants produce bulbs or runners.
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When do clones of animals occur?
1) Naturally when the cells in an embryo seperate (identical twins). 2)Artificially when the nucleus of an adult body cell is transferred into an unfertilised denucleated egg cell and implanted into another organisms uterus.
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Name two different types of stem cells.
1) Adult stem cells (partially specialised) which can develop into many but not all cells. 2) Embryonic stem cells (unspecialised) which can develop into any cell.
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How do adult and embryonic stem cells have potential to treat some illnesses
They are only partially or fully (resectively) specialised and so can be grown into specialised cells for any part of the body. This could treat illness which affects cells.
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When do cells become specialised?
The majority of cells in a multicellular organism become specialised during the early stages of its development.
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Other cards in this set

Card 2


What do genes carry?


Instructions for making protiens.

Card 3


What are the two different types of protien called?


Preview of the front of card 3

Card 4


What are genes made of and where are they found in the nucleus?


Preview of the front of card 4

Card 5


Describe the difference between genetic and enviromental characteristics.


Preview of the front of card 5
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