Your SlideShare is downloading. ×
  • Like
  • Save
Chapter 19 Heredity Lesson 2 - Present day understanding on heredity based on Mendel’s Experiments
Upcoming SlideShare
Loading in...5

Thanks for flagging this SlideShare!

Oops! An error has occurred.


Now you can save presentations on your phone or tablet

Available for both IPhone and Android

Text the download link to your phone

Standard text messaging rates apply

Chapter 19 Heredity Lesson 2 - Present day understanding on heredity based on Mendel’s Experiments



Published in Education , Technology
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
No Downloads


Total Views
On SlideShare
From Embeds
Number of Embeds



Embeds 0

No embeds

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

    No notes for slide


  • 1. Present Day Understanding on Heredity based on Mendel’s Findings
  • 2. Key Concepts:
    • In cells, DNA molecules are packaged into chromosomes
    • An unduplicated chromosome consists of one DNA molecule and many associated proteins ( histones )
    • The total number of chromosomes in a body cell ( somatic cell ) is the diploid number (2n)
    • The human diploid number is 46 and consists of a pair of sex chromosomes and 22 pairs of autosomes (non-sex chromosomes)
    • The diploid number consists of one set of chromosomes from each parent
    • The same two chromosomes from different parents = a homologous pair
  • 3. DNA DNA is a double helix formed by base pairs attached to a sugar-phosphate backbone. http://
  • 4.  
  • 5. Chromosomes
    • Thread-like structure found in the nucleus on which genetic material is organized
    • Carry the information for making new animal or plant bodies
    • This information is carried in DNA
    Karyotype: A photomicrograph of an individual's chromosomes arranged in a standard format showing the number, size, and shape of each chromosome type
  • 6. Homologous chromosomes
    • Homologous chromosomes mean that diploid cells have two copies of each gene, with one copy coming from mom and one copy coming from dad!
    • - However, the sequences of the two genes do not have to be identical
  • 7. Genes - small fragment of DNA in a chromosome where a piece of genetic (hereditary) info is stored - gene locus = place on the chromosome where the gene resides; controls a particular trait e.g. colour, height, etc.
  • 8. Allele
    • the sequences of the two genes do not have to be identical
    • alternative forms of the same gene
    • - e.g. gene for height may have 2 alleles: short and tall
    Skin Color Height
  • 9. Genotype = the specific combination of alleles; represented by letters Phenotype = what trait looks (acts) like
  • 10. Pair of homologous chromosomes A gene locus A pair of alleles 3 pairs of alleles Test yourself
  • 11. Relationship between DNA, Chromosomes and Genes
  • 12.  
  • 13.  
  • 14. C c Fertilization produces heterozygous offspring meiosis II meiosis I (chromosomes duplicated before meiosis) Homozygous dominant parent Homozygous recessive parent gametes gametes Mendel’s Theory of Segregation C C C C C C C C C C C C C C c c c c c c c c c c c c c c
  • 15. Lesson Objectives
    • (f) explain co-dominance and multiple alleles with reference to the inheritance of the ABO blood group phenotypes - A, B, AB, O, gene alleles I A , I B and I O
    • (g) describe the determination of sex in humans - XX and XY chromosomes
    • (h) describe mutation as a change in the structure of a gene such as in sickle cell anaemia, or in the chromosome number, such as the 47 chromosomes in a condition known as Down Syndrome
    • (i) name radiation and chemicals as factors which may increase the rate of mutation