Topic 3 - genetics Flashcards
What is meiosis?
- produce haploid gamete cells
- only have one copy of each chromosome.
- forms four non-identical cells from one cell.
Describe meiosis
- diploid parent cell with 46 chromosomes
- Chromosomes make non- identical copies of themselves
- similar chromosomes pair up ( still non- identical)
- sections of DNA get swapped
- pair of chromosomes divide & become daughter cells
- chromosomes divide again into 4 haploid gamete non- identical cells ( males make sperm and women make egg)
Differences between mitosis and meiosis
- meiosis produces 4 daughter cells & mitosis produces 2 daughter cells
- mitosis produces genetically identical cells, meiosis produces genetically different
- mitosis produces diploid cells and meiosis produce haploid cells
Structure of DNA
- made up of nucleotides w/ one sugar and one phosphate molecule
- complimentary matching base pairs A,T & C,G
- double helix twist
What is a gene?
- short section of DNA. Each gene codes for many amino acids, which are joined together to make a specific protein.
- There are 20 types of amino acid
What is a genome?
- all the genetic information (DNA) of a single organism
Describe How to extract DNA from a fruit
- mix cold water, half a teaspoon of salt and washing up
liquid– heat mixture for 5-10 minutes. - chop into small pieces & Pulverise fruit
- Add solution from Step 1 to fruit.
- Filter solution and pour filtrate into a test tube.
- Add pineapple juice to filtrate and allow to rest for a few minutes.
- Add cold ethanol to the solution and wait.
– white precipitate should form from fruit– this is the DNA
Why do we add (pineapple) juice and ethanol in the ‘how to extract DNA from fruit experiment.’
- juice
- contains an enzyme that breaks down proteins attached to DNA.
- helps us see DNA more clearly
- ethanol
causes DNA to precipitate out of the solution - makes it visible
What is the non coding part of DNA?
- doesn’t code for proteins– some responsible for determining if gene is used to form a protein or not
What is a polypeptide ?
- amino acids linked by peptide binds
Difference between phenotype & genotype ?
- genotype is the set of genes in our DNA which is responsible for a particular trait
- phenotype is the physical expression, or characteristics, of that trait (one you can see)
How can Mutations change the sequences of bases in DNA?
- base is inserted into the code
- base is deleted from the code
- base is substituted
How can Mutations change the sequences of bases in DNA?
- A base is inserted into the code
- A base is deleted from the code
- A base is substituted
Mendel’s pea experiments
- got smooth peas, wrinkled peas, green peas & yellow peas and observed offspring to see which characteristics they’ d inherited
- Offspring have some characteristics that parents had because they
inherit ‘hereditary units’ from each. - unit received from each parent.
- can be dominant or recessive, cannot be mixed together.
Different between dominant and recessive gene
- dominant
Only one of two alleles needed for it to be expressed - recessive
Two copies needed for it to be expressed
What is zygote?
- stage of development right after fertilisation from 2 gamete cells
- diploid cell
What are alleles?
- different from of the same gene
- allele that codes for a damaged part of a protein can cause an illness
what is codominance ?
2 dominant alleles that can be expressed together in the same individual.
What is genetic variation?
different characteristics because of random mutation and sexual reproduction.
- produces new phenotypic characteristics,
What is environmental variation?
- characteristics changed by organism’s environment, but changes are generally not heritable
Benefits of human genome
- improved understanding genes linked to different types of disease
- helped in treatment of inherited disorders
- helped in tracing human migration patterns from the past.
Effects of genetic mutation on phenotype
- some mutations, can rarely affect phenotype - some do though
- changing one base can change one amino acid in a protein. If an enzyme, can change shape of the active site — substrates can no longer fit
Explain natural selection
- process whereby organisms better adapted to their environment tend to survive and produce more offspring
- leads to evolution
Family pedigree symbols
- square means man, coloured square means infected man, half coloured in means recessive, carries but doesn’t affect him – same w/ women but they are circles
ABO Blood Group Inheritance
- A and B are co dominant and O is recessive
- O is universal donor
Benefits of human genome project?
- understanding of genes linked to different types of disease
- help treatment of inherited disorders
- help in tracing human migration patterns from the past
Describe protein synthesis
DNA contains the genetic code for making a protein, but cannot move out of the nucleus as it is too big.
- mRNA nucleotides are then joined together, creating a new strand called the mRNA strand. This is a template of the original DNA.
- enzyme called RNA polymerase binds to non-coding DNA located in front of a gene on the DNA strand.
- The two strands of DNA pull apart from each other, and mRNA nucleotides match to their complementary base on the strand. It becomes (A,U and C,G)
- mRNA then moves out of the nucleus to the cytoplasm and onto structures called ribosomes.
- At the ribosomes, the bases on the mRNA are read in triplets to code for an amino acid (first three bases code for one amino acid etc).
- corresponding amino acids are brought to the ribosomes by tRNAs - transport RNAs
- . These amino acids connect together to form a polypeptide
- When chain is complete the protein forms a unique 3D structure, which is the final protein.
