LIFE SCIENCE FOR GRADE 11 AND 12 (GENETICS: DNA, INHERITANCE AND GENETIC DESEASES)

1. GENETICS: DNA,
INHERITANCE AND
GENIC DISEASES
COMPLILED BY: SITHEMBISO BRIDGET NXUMALO
(201122793)

2. GENETICS
• Field of Biology that studies how
characteristics are transferred
from parent to offspring
• Begins, chronologically, with the
work of Austrian monk Gregor
Johann Mendel in the 1850-60s.
• by mrjurkiewicz on Nov 29, 2010

3. MENDEL: EDUCATION
• In fact, Mendel was a welleducated scientist
• Studied physics and
mathematics at the
Olmütz Philosophical
Institute at the University
of Vienna, beginning in
1851
• by mrjurkiewicz on Nov
29, 2010

4. MENDEL: LEGACY
• by mrjurkiewicz on Nov 29,
2010

5. LOCATION OF DNA IN
A CELL
• Chromatin is a complex of DNA and
protein, and is found in the nucleus
of eukaryotic cells.
• Histones are proteins that are
responsible for the first level of DNA
packing in chromatin
• The chromatin network in the
nucleus of a cell will coil up tightly
during cell division and form
individual chromosomes.

6. • Chromosomes are always
duplicated during this process (2
sets of identical genetic information to
ensure each cell receives identical
genetic info to the parent cell during
cell division).
• A duplicated chromosome consists
of 2 chromatids attached to each
other by a centromere.
• Each chromatid consists of several
genes.
• Genes consists of a long DNA strand.

7. LOCATION OF DNA IN
A CELL
Locus: Position of gene on chromos

8. A DNA double helix structure

9. INHERITANCE

10. is the process in which traits are passed
from parents to offspring
is the study of heredity

11. CHARACTERS OR TRAITS ARE RESEMBLANCES OR
DIFFERENCES WHICH CAN BE:
Seen e.g.
eye colour
flower colour
Tested for e.g.
blood groups
colour blindness

12. LET’S REVISE:
• Genes:
 control the characteristics of living organisms
 are carried on the chromosomes

13. • Chromosomes are in pairs, one from each parent

14. • Genes are in pairs
• Genes controlling the same characteristics occupy identical positions on
corresponding chromosomes
• The gene pairs control one characteristic
gene for
eye colour
gene for
nose shape
gene for
making insulin

15. The genes of a corresponding
pair are called alleles
Alleles are alternative
forms of the same gene
Gene
Homologous chromosomes have the same
length and carry the same gene sequences

16. GENETIC DISEASES

17. MUTATIONS
• A mutation is a change in a gene
• A mutation can only be inherited in it occurs in a sex cell
• Effects of mutations can be:
•
Positive
•
Negative
•
Neutral

18. CHROMOSOME MUTATIONS
.Deletion – loss of a piece of a chromosome
. Translocation – a piece of one chromosome
breaks off and reattaches to a nonhomologous
chromosome
Nondisjunction – chromosome fails to
separate from its homologue during meiosis

19. GENE MUTATIONS
• Point Mutation – one nucleotide is changed in the DNA sequence
•
Substitution
•
Deletion
•
Insertion

20. GENE MUTATIONS
• Insertion – one or more
nucleotides are added to a gene
• Substitution – one nucleotide
replaces another

21. GENETICAL TERMINOLOGIES
• Genes – parts of chromosomes (DNA) that control
specific characteristics

22. MOLECULAR GENETICS
• How many of each type of
chromosome does a cell have?
• TWO! (Chromosomes
come in pairs.)

23. VOCABULARY
• Alleles – several
alternate forms of a
gene that cause
different traits
• Example: one allele may
cause blonde hair, while
another causes black

24. ALLELES
• Organisms ALWAYS have
two alleles (one on each
chromosome)
• Alleles can be either
dominant or recessive

25. ALLELES
• Letters are used to represent alleles
• Capital letters = dominant genes
• Lowercase letters = recessive genes

26. ALLELES
• Example: short hair is
dominant over hairless
in dogs
• Short hair: H
• Hairless: h

27. ALLELES
• Since organisms have two of each
type of chromosome (with one
allele on each), genes must be
represented by two letters
• Examples: HH, Hh, or hh

28. ALLELES
• Dominant alleles mask
recessive
• HH – 2 dom.
• Hh – 1 dom., 1 rec.
• hh – 2 rec.

29. ALLELES
• Dominant alleles mask recessive
• HH – dominant trait
•
Short hair
• Hh – dominant trait
•
Short Hair
• hh – recessive trait
•
Hairless

30. GENETICAL TERMINOLOGIES:
• Homozygous – two of the
same alleles
• Homozygous dominant - two
dominant alleles
• Homozygous recessive – two
recessive alleles

31. VOCABULARY
• Heterozygous – two
different alleles
• Usually one is dominant
and one is recessive

32. EXAMPLE
• Long necks in giraffes are
dominant to short necks (N
and n)
• Genes vs. displayed trait

33. GENETICAL TERMINOLOGIES:
• Genotype – genetic makeup of
an individual (example: Nn or
nn)
• Phenotype – observed
characteristics (example: long
or short neck)

34. REFERENCE LIST:
Campbell, J. & Recee, C. (2010). Biology: Genetics. (8th edition). Peason: Benjiam Publishers.
Mjnap. (11 months). geneticdiseasespresentation-130311073210-phpapp01.pptx
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4099263&AWSAccessKeyId=AKIAIW74DRRRQSO4NIKA. Accessed: 06/03/2014
SECBIO. (5months). genetics-130907092527-.pptxhttp://s3.amazonaws.com/pptdownload/genetics-130907092527-.pptx?response-content-disp. Accesed : 06/03/2014.
SPITZECA. (2011). geneticspresentationsuggestededits-110831055527-phpapp02
(1).pptxhttp://s3.amazonaws.com/ppt-download/geneticspresentationsuggestededits110831055527-phpapp02.pptx?response-contentdisposition=attachment&Signature=SUVNHZLSIXe6lQJp%2BjDafYz8HPE%3D&Expires=13940
99134&AWSAccessKeyId=AKIAIW74DRRRQSO4NIKA. ACCESSED: 06/03/2014