Topic 3- Genetics Flashcards
What is the structure of DNA?
- a polymer made up of two strands coiled into a double helix.
- made of sugar phosphate backbone, sugar and one of the 4 bases.
- the nucleotides units repeat to make up the DNA polymer.
- complementary bases pairs held together by weak hydrogen bonds.
What is sexual reproduction?
Sexual reproduction- when genetic information from two organisms is combined to produce offspring which are genetically different to either parent.
1. Parents produce haploid gametes (reproductive cells).
2. Gametes fuse at fertilisation.
3. A diploid zygote (fertilised egg) is produced. (Contains chromosomes from both parents.
4. The zygote divides by mitosis and becomes an embryo.
Chromosomes- long molecules of DNA that normally comes in pairs.
Haploid- containing half the number of chromosomes of normal cells.
Diploid- containing a full set of chromosomes.
What is meiosis?
Meiosis- is a type of cell division that produces four haploid daughter cells.
1. Duplicated chromosomes become one copy of each chromosome (division 1).
2. One copy of each chromosome become haploid gametes (division 2).
All the gametes produced by meiosis are genetically different.
How to extract DNA from fruit?
- Mash fruit (+detergent and salt)
Detergent- breaks down the cell membranes to release DNA. Salt makes the DNA stick together. - Mix well.
- Filter the mixture +ice cold ethanol)
- The DNA appears as a stringy white precipitate. Fish it out with a glass rod.
What are some Genetic terms?
Genome- All of an organisms DNA.
Gene- A small section of DNA found on a chromosome that codes for a particular protein.
Allele- A version of a gene.
Dominant- An allele that is always expressed.
Recessive- An allele that is only expresses when two copies are present.
What are some more Genetic terms?
Homozygous- Both of an organisms alleles for a trait are the same.
Heterozygous- An organisms alleles for a trait are different.
Genotype- An organism’s combination of alleles.
Phenotype- the characteristics an organism has.
-Some characteristics are controlled by a single gene but most are controlled by multiple genes.
- Body cells have two alleles of every gene- one on each chromosome.
What is MonoHybrid Inheritance?
Inheritance of a single characteristic.
It is shown by monohybrid cross, which is used to work out the probability of outcomes for dominant and recessive traits.
What is Sex determination?
- Human body cells have 23 pairs of chromosomes.
- The 23rd pair determines sex.
Female gametes- XX
Male gametes- XY on punnet squares.
What is Family Pedigrees?
Horizontal lines link parents.
Vertical lines connect parents to children.
E.g that is used on Family Pedigrees:
Cystic Fibrosis- a genetic disorder of the cell membranes caused by a recessive allele.
What is Variation?
Variation- differences in the characteristics of organisms.
Mutation- a random change is the base sequence of DNA. ( the base sequence of a gene determines what protein is made).
Genetic Variation:
Differences in the genes individuals inherit causes genetic variation within a population- variation from sexual reproduction.
Mutations cause theses differences in genes.
- Mutations usually don’t have any effect on phenotypes.
What is environmental and genetic variation?
Environmental variation:
Differences in the conditions in which organisms develop cause variation- they get acquired characteristics. E.g leaf colour
Genetic and environmental variation:
For most characteristics, variation is caused by both genetic and the environment. E.g plant height
What is the Human Genome Project?
The complete human genome has been worked out.
Genes linked to diseases can be identified…
This helps with:
Prediction and prevention- knowing which genes predispose people to what diseases,can help doctors tailor advice and treatments.
Testing and treatments from inherited disorders- people can be tested early and we can develop better treatments.
Developing new and better medicines- drugs and dosages can be tailored to individuals.
Potential for more effective treatments with fewer side effects.
