inheritance

The study of how genetic information passes from parent to offspring

Genetic information is carried by DNA, by chromosomes

Chromosomes

• Made up of DNA

• In the cell nucleus you find a chromosomes

• Inside the chromosome we have a combination of DNA bases

• Carry gene

DNA

• A length of the DNA is a gene

DNA gives you chromosomes which give you genes

Homologous chromosomes

• Carry the same genes

If this gene instruction to pass it can only pass through chromosomes

Every quality you have on you now is expressed because of some gene in your body

Sex determination

• The outcome the way it comes out shows the probability of

• Genetic diagram

  • Shows the passage of features from parent to child

• Parent phenotype

  • Physical features a person has

    • So and so has brown eyes

  • Male x female

• Parent genotype

  • The makeup of the genes of that person

  • XY x XX

  • Meiosis

    • The making of gametes

    • The sperm and the ovum

  • Genetic diagram. Pannel square

• Genotype determines the phenotype of a person

• Ratio is always based on the phenotype not genotype

Monohybrid Inheritance

• Single factor inheritance

• Single feature inheritance

  • B = brown eyes

  • b = black eyes

• All Capital Case letters = dominant gene

• All lower case letters = recessive gene

• An allele

  • An alternative form of a gene

    • B is an allele for b

    • They are both talking about eye colour 

    • The gene is one or the same in eye colour  but there are 2 forms of eye colour

      • Brown + black

    • Whatever colour  it is, we are talking about the same gene

  • There are 3 possible combinations of the genes:

    • BB - homozygous dominant

    • Bb - heterozygous 

    • bb - homozygous recessive

F1 + F2

• F1 is first filial generation

  • The generation/offspring from the first set of parents who mated

• F2 is second filial generation

  • These are offspring/generation made by crossing two F1 offspring

Test cross

• Finds the unknown genotype of a parent

Codominance

• This is where both allele in heterozygous contribute to the phenotype of an organism/offspring

  • Both alleles are expressed in the phenotype

  • Both traits are seen in the physical appearance

  • This is because the dominant masks the recessive one

• Examples of codominance

  • Flower[four o' clock] with three different colours

    • Red

    • White

    • Pink

  • Genetic cross to show how a red flower and white flower give rise to a pink one

Blood group inheritance

• Notation: Ia or I^b or Io

• Blood group system is called ABO system

• Alleles A+B are codominant

• Alleles A+B are dominant to O

• Allele O is recessive to A+ b

Chromosomes before cell division and same chromosomes undergoing cell division

The above chromosones are called homologous chromosones. They are the same and caryy the same

The one chromosone is made of chromatid and chromatid

They are sister chromatids

When the cell is not dividing

1 chromosone is made of 2 chromotid