Topic B3 Flashcards
Monohybrid inheritance
Inheritance of a single characteristic
How many chromosomes do human body cells have?
23
Which chromosome pair determines the sex?
23rd
Female gametes
XX
Male gametes
XY
Family pedigree
-Show how genetic disorders are inherited
-horizontal lines link parents
-vertical lines connect parents to children
Variation
Differences in characteristics of organisms
Mutation
-Random change to order of bases in DNA (order determines what protein is made)
-not all mutations affect phenotypes
Genetic variation
Differences in the genes individuals inherit
Environmental variation
Variation due to conditions organism developed in- acquired characteristics e.g leaf colour
The Human Genome Project
-complete human genome worked out
-genes linked to diseases can be identified
What does the human genome project help with?
-prediction and prevention
-treatment and genetic disorders
-developing medicines
DNA
Polymer made up of 2 strands coiled into a double helix
Parts of a DNA strand
-phosphate
-nucleotide (repeating, make up DNA polymer)
-sugar
-bases
Base pairs held together by weak hydrogen bonds
AT
CG
Stages of sexual reproduction
- Parents produce haploid gametes (sex cells)
- Gametes combine during sex
- Diploid zygote (fertilised egg) is produced, contains csomes from both parents
Chromosomes
Long molecules of DNA that normally come in pairs
Haploid
Containing 1 copy of csome 
Diploid
Containing two copies of each chromosome, normal cells
Meiosis
Cell division that produces four haploid daughter cells
Stages of meiosis
-DNA copied
-Division 1, 1 copy of each chromosome produced
-Division 2, 4 haploid gametes produced
Stages of extracting DNA from fruit
- Mash fruit+detergent (breaks down cell membranes to release DNA)+salt (makes DNA stick together)
- Mix well
- Filter the mixture+ice cold alcohol
- DNA appears as a white stringy precipitate. Fish out with glass rod
Genome
All of an organism’s DNA
Gene 
A small section of DNA 
Allele
A version of a gene
Dominant
An allele that is always expressed (used to make protein)
Recessive
An allele that is only expressed when 2 copies are present
HomozygouS
Alleles for a trait are the same
HeTerozygous
An organisms alleles for a trait are different
Genotype
An organisms combination of alleles
Phenotype
The characteristics an organism has