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Biology (P1)
Genetics
| Question | Answer |
|---|---|
| What is meiosis used for? | To produce haploid gametes |
| What is meiosis? | The formation of four non-identical cells from one cell |
| Why are gametes genetically different? | Because the chromosomes are shuffled during the process resulting in random chromosomes ending up in each of the four cells |
| How is an embryo formed after 2 gametes fuse? (3) | Cell divides by mitosis, more and more cells are produced and an embryo is formed, the cells take on differentiation |
| What is DNA and what is it made up of? | Polymer that is made up of nucleotides. |
| What is a nucleotide made up of? (3) | One sugar molecule, one phosphate molecule and one of the 4 types of organic bases |
| DNA is a polymer made up of 2 coiled strands to form a... | Double Helix |
| What does the word genome describe? | All the genetic information (DNA) of a single organism. |
| What is a gene? (3) | Short section of DNA, codes for many amino acids, joined together to make a specific protein |
| How do we extract DNA from fruit? (4) | Mash fruit and place in a beaker with detergent and salt to mix, filter the mixture, add ice cold alcohol to the filtered mixture, DNA will appear stringy and white |
| Give a definition of chromosome. | Structure in nucleus, made up of long strand of DNA |
| What is an allele? | Different form of gene, humans have 2 alleles for each gene from each parent |
| What is a dominant allele? | Only one out of 2 is needed for it to be expressed and for corresponding phenotype to be observed |
| What is a recessive allele? | 2 are needed for it to be expressed and for corresponding phenotype to be observed |
| What is homozygous? | Both inherited alleles are the same (e.g 2 recessive or 2 dominant) |
| What is heterozygous? | When one inherited allele is dominant and one is recessive |
| What is a genotype? | Combination of alleles someone has (Aa) |
| What is a phenotype? | Physical characteristics in an individual (eye colour, hair colour) |
| What is a zygote? | Immediately after fertilisation, diploid cell formed from fusion of 2 haploid gametes |
| Why do alleles result in differences in inherited characteristics? | Different alleles code for different forms of the same protein |
| How do we draw a punnett square? | 2 vertical and 2 horizontal, both alleles of father on the left, both alleles of mother on top |
| In human body cells 22/23 pairs of chromosomes control characteristics, what does the 23rd pair control? | Sex determining genes |
| What chromosomes do males and females have? | Males= XY Females = XX |
| What are most phenotypic features the result of? | Multiple genes acting together, not single gene inheritance |
| When it comes to genetic variation, different characteristics can arise as a result of both... (2) | Random mutation and sexual reproduction |
| How does random mutation work in gametes? | Produce offspring with brand new phenotypic features. |
| What does sexual reproduction cause the offspring? | Have combination of characteristics from mother and father |
| Give an example of environmental variation. | A child not having all the necessary nutrients cannot grow to their full height, however this doesn't change the height potential within their genetics |
| Give 3 positive benefits of the human genome project. | Improved understanding of genes linked to disease, helped in treatment with inherited disorders and helped in tracing human migration patterns from the past |
| By mapping the entire human genome, what can we better understand? (2) | Which genes cause inherited disorders and which genes are linked with each other. |
| What does the arise in mutations cause? | Extensive genetic variation within a population of species |
| In what 3 ways can genetic mutation have on the phenotype? | Some have no effect, some have small effect and some have a significant effect |
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