B1 Question 1 Foundation

Transcription

1 B1 Question 1 Foundation The nucleus controls the activities of a cell. The instructions for how an organism develops i.e. the genes are found in the nuclei of its cells

2 B1 Question 2 Foundation The genes have a specific job. Genes are the instructions for proteins

3 B1 Question 3 Foundation Chromosomes are very long molecules made from DNA Each human cell has 23 pairs of chromosomes

4 B1 Question 4 Foundation Pair of chromosomes allele for brown eyes allele for blue eyes Chromosomes in a pair carry the same genes in the same place, but that there may be different versions of genes called alleles An individual usually has two alleles for each gene Homozygous: the two alleles of a gene are the same Heterozygous: the two alleles of a gene are different

5 B1 Question 5 Foundation Children may have some similarity to their parents because genes/chromosomes are inherited from both parents.

6 B1 Question 5 Higher Individuals differ in all sorts of ways, even when they are offspring of the same parents. These differences are called variation. Most characteristics, such as height, are determined by several genes working together. They are also influenced by environmental factors. Huntington s disorder is caused by a dominant allele, written as H You only need to inherit one copy of the faulty allele to have Huntington s disorder. You can inherit Huntington s disorder if one or both of your parents carry the faulty allele, because it is a dominant allele.

7 B1 Question 6 Foundation Huntington s disorder is caused by a dominant allele. The symptoms usually develop in middle age, and include tremors, clumsiness, mood changes, memory loss and the inability to concentrate People with Cystic Fibrosis produce abnormally thick and sticky mucus in their lungs and airways. As a result, they are more likely to get respiratory infections. Daily physiotherapy helps to relieve congestion, while antibiotics can fight infection. The disease blocks tubes that take enzymes to the gut meaning food is not digested properly, leaving the person short of essential nutrients.

8 B1 Question 7 Foundation You can show determination of sex using genetic diagrams called Punnett Squares. Notice that half of the babies should be male, and half female. Individual families can have more or less of each sex, but in a large population there will be roughly equal numbers of boys and girls.

9 B1 Question 8 Foundation Cystic fibrosis (CF) is caused by a recessive allele. You need to inherit two copies of the faulty allele to be born with CF. If you have just one copy, you are a carrier, but will not experience any symptoms. If two carriers have a child together, there is a one-in-four chance of passing on the disorder.

10 B1 Question 9 Foundation Scientists are now able to test adults and foetuses for alleles that can cause genetic diseases However, the scientific information produced raises many issues that science cannot address There are different views as to why these tests should or shouldn't be carried out for: find out if the baby has the disease find out if the baby is a carrier may decide to terminate the pregnancy against: risk of miscarriage; results may not be reliable; it s better not to know