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Genes Inheritance
Revision for the Second Year 8 Test
Question | Answer |
---|---|
What are alleles? | These are different versions of the same gene. For example there are different alleles for eye colour. |
What is a chromosome? | This is a thread like structure containing highly coiled DNA. |
What does DNA stand for? | Deoxyribonucleic acid. |
What is a dominant allele? | The strongest allele in a pair. |
What is the function of DNA? | It contains the code that determines all the inherited characteristics of a living organism. |
What are gametes? | In humans, these are eggs and sperm, They each contain half the number of chromosomes of each parent and combine during fertilisation. |
What is genetic modification? | This is manipulating an organism's DNA in a laboratory. |
What does 'genotype' mean? | This describes the pair of alleles that an organism has for a certain characteristic. |
What is the meaning of 'heterozygous'? | An organism that has two different alleles for the same characteristic. |
What does 'homozygous' mean? | This is an organism that has two identical alleles for the same characteristic. |
What is the human genome? | The complete sequence of human genes. |
What are inherited characteristics? | Features that are passed from parents to offspring. |
What is mutation? | A change in DNA. |
What is the function of a nucleus? | This controls the cell's activities, growth and reproduction. |
What is a person's phenotype? | This is their outward appearance. |
What does 'recessive' mean? | This is the weaker allele of a pair. An organism needs to have two of these for a characteristic to show e.g. blue eyes. |
What shape is DNA? | A double helix. |
Which bases pair up? | A pairs with T, C pairs with G. (Apples grow on trees, cars go in a garage). |
Can you remember what ATCG stand for? | Adenosine, Thymine, Cytosine, Guanine |
What do the blocks of three bases code for? | Amino acids |
What do amino acids join to form? | Protein molecules. |
If you stretched out all the DNA in your body how far would it go? | 9 million kilometres. |
How long is the DNA in one human cell nucleus? | 2 metres |
How many chromosomes do humans have? | 46 chromosomes (23 pairs) |
What is a gene? | This is a section of DNA that contains the instructions for an inherited characteristic. E.G. eye colour. |
Where did each pair of your chromosomes come from? | One of the pair came from your father and the other one came from your mother. |
How many chromosomes do human eggs and sperm have? | 23 |
How many genes does the human genome contain? | 24,000 |
If a person has brown eyes and are heterozygous for eye colour, what would their genotype be? | Bb |
What is the genotype of someone with blue eyes? | bb |
What is the genotype for someone who is homozygous for brown eyes? | BB |
If a brown eyed person (BB) and a blue eyed person (bb) have children, what colour eyes could the children have? | Brown eyes. Bb |
If a brown eyed person (Bb) and a blue eyed person (bb) have children, what colour eyes could the children have? | They could have brown eyes (Bb) or blue eyes (bb). |
If two heterozygous brown eyed parents (Bb) have children. What could the children's genotypes be? | BB, Bb or bb. |
What is special about identical twins? | They have identical DNA. |
What are some symptoms of Cystic Fibrosis? | Problems with the lungs due to excessive mucous. Problems in the digestive system for the same reason. |
Cystic Fibrosis is caused by a recessive allele (f). What genotype does a person have to have in order to have the disease? | ff |
What do we call a person who has the recessive allele for Cystic Fibrosis plus the dominant normal allele Ff? | A carrier - because they don't actually have the disease but they carry the allele for it. |
What does 'polydactyly' mean? | Many digits. |
Polydactyly is a dominant allele. Why would it be impossible for someone with polydactyly to have two normal parents. | |
Why aren't all twins identical? | Identical twins came from one egg and have identical DNA. Fraternal twins came from two eggs (one egg each) and are no more similar than brothers and sisters. |
Why can't you tell whether twins are identical or fraternal from their weight (mass)? | Weight is not controlled by genes. It is an environmental factor. Weight is determined by how much you eat, what you eat and how much you exercise. |