B13 (Reproduction and Genetics) Flashcards
Gametes
Sex cells and contain 23 chromosomes, one of each from the mother and father
Chromosomes
Very long molecules of DNA, found in the nucleus
Alleles
different versions of the same gene, that codes for a different version of a characteristic
Dominant
When an alleles coded by a phenotype is only in one of the chromosomes
Recessive
When an Alleles coded by a phenotype is in both chromosomes
Homozygote
Pair of alleles that produces the same characteristics
Heterozygote
Pairs of alleles that produce different characteristic
Genotype
Description of the pair of alleles present for characteristics
Phenotype
Physical expression of the alleles
Sexual reproduction
- genetic info transferred 2 different organisms
- eg. Egg and sperm fertilise
Asexual reproduction
- only one parent
- this means offspring is a clone of parent
- occurs through mitosis
4 Advantages of Sexual (over Asexual)
- variation of offspring
- increased chance of surviving if change environment
- speed up natural selection and pass desirable genes
- increases food production as could destroy genetic diseases
3 advantages of Asexual (over sexual)
- only need one parent
- uses less energy as don’t need to find mate
- faster than sexual
5 stages of Meiosis (Sexual)
1) Cells divides and duplicates forming 2 chromosomes with genetic info
2) Chromosomes line up in centre
3) Paris pulled apart with parts from each parent
4) 2nd division as chromosomes line up again and pul apart
5) four gametes (daughter cells) each with single set of chromosomes and genetically different
3 examples of reproduction both ways
- malaria as reproduce sexually, but asexually in human host
- fungus has asexual spores to produce and asexual spores for variation
- Strawberry produces seeds sexually, then asexually for clones
Nucleotides
Strands of polymers that are madd up of repeating units
3 Structures of Nucleotides
- one sugar molecule
- one phosphate molecule (backbone)
- one ‘base’ and they make up double helix
Bases that join to the sugar
A-T
C-G
- these are complementary base paring
Amino acids ordering in structure of DNA
- 3 bases of the gene decide the order of amino acids
- they join to make many proteins depending on the order of the gene
Non-coding parts of DNA
- don’t code for proteins and switch genes on and off to make proteins
Ribosomes for DNA
- where proteins are made using DNA code
- mRNA copies the DNA and is the messenger between nucleus and ribosomes for the amino acids
3 functions of proteins
- enzymes
- hormones
- structure proteins to strengthen tissues
Human Genome Project
- complete map of 20,000 genes
- linkage maps track inherited traits/ genetic diseases
- insight so scientists can cure diseases
5 stages of completing a punnet square
1) phenotype (Brown Eyes)
2) genotype, parent (BB X bb)
3) Gametes (B,B x b,b)
4) Punnet Square
5) Ratios
Cystic Fibrosis
- recessive trait
- genetic disorder of cell membrane
- build up mucus in air passage and pancreas
Polydactyly
- dominant trait
- genetic disorder where you have extra fingers or toes
Embryo Screening
- IVF embryos in lab and implanted in womb
- take out cells to study genetic disorders
- embryos with ‘bad’ alleles destroyed
3 Adv/ 3 Disadv of embryo screening
- stops suffering, treating disorders costs money for government, laws to stop it going too far
- implies people with disorders are undesirable, everybody may want to do it, exspensive
Male and Female Chromosomes
- Males have X and Y
- Females have X and X
Mutations of DNA
- random changes of the DNA
- changes the sequence of bases and changes in the proteins
- caused by genetic and other factors like radiation
3 types of mutations
- insertions where a new base is inserted, with changes the code
- deletions are where random bases deleted
- substitutions where random bases are changed to a different base
