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LIFE SCIENCE FOR GRADE 11 AND 12 (GENETICS: DNA, INHERITANCE AND GENETIC DESEASES)
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GENETICS: DNA, INHERITANCE AND
GENIC DISEASESCOMPLILED BY: SITHEMBISO BRIDGET NXUMALO
(201122793)
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
MENDEL: EDUCATION
• In fact, Mendel was a well-educated scientist
• Studied physics and mathematics at the Olmütz Philosophical Institute at the University of Vienna, beginning in 1851
• by mrjurkiewicz on Nov 29, 2010
MENDEL: LEGACY
• by mrjurkiewicz on Nov 29, 2010
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.
• 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.• A string of DNA coiled around a few
histones is called a nucleosome.
LOCATION OF DNA IN A CELL
Locus: Position of gene on chromosome
A DNA double helix structure
INHERITANCE
is the study of heredity
is the process in which traits are passed from parents to offspring
CHARACTERS OR TRAITS ARE RESEMBLANCES OR DIFFERENCES WHICH CAN BE:
Seen e.g.
eye colour
flower colour
Tested for e.g. blood groupscolour blindness
LET’S REVISE:• Genes:
control the characteristics of living organisms
are carried on the chromosomes
• Chromosomes are in pairs, one from each parent
• 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 fornose shape
gene for making insulin
The genes of a corresponding pair are called alleles
Homologous chromosomes have the same length and carry the same gene sequences
Alleles are alternative forms of the same geneAlleles are alternative forms of the same gene
Gene
GENETIC DISEASES
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
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
GENE MUTATIONS
• Point Mutation – one nucleotide is changed in the DNA sequence
• Substitution
• Deletion
• Insertion
GENE MUTATIONS
• Insertion – one or more nucleotides are added to a gene
• Substitution – one nucleotide replaces another
GENETICAL TERMINOLOGIES
• Genes – parts of chromosomes (DNA) that control specific characteristics
MOLECULAR GENETICS
• How many of each type of chromosome does a cell have?
• TWO! (Chromosomes
come in pairs.)
VOCABULARY
• Alleles – several alternate forms of a gene that cause different traits
• Example: one allele may cause blonde hair, while another causes black
ALLELES
• Organisms ALWAYS have two alleles (one on each chromosome)
• Alleles can be either dominant or recessive
ALLELES
• Letters are used to represent alleles
• Capital letters = dominant genes
• Lowercase letters = recessive genes
ALLELES
• Example: short hair is dominant over hairless in dogs
• Short hair: H
• Hairless: h
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
ALLELES
• Dominant alleles mask recessive
• HH – 2 dom.
• Hh – 1 dom., 1 rec.
• hh – 2 rec.
ALLELES
• Dominant alleles mask recessive
• HH – dominant trait• Short hair
• Hh – dominant trait• Short Hair
• hh – recessive trait• Hairless
GENETICAL TERMINOLOGIES:
• Homozygous – two of the same alleles
• Homozygous dominant - two dominant alleles
• Homozygous recessive – two recessive alleles
VOCABULARY
• Heterozygous – two different alleles
• Usually one is dominant and one is recessive
EXAMPLE
• Long necks in giraffes are dominant to short necks (N and n)
• Genes vs. displayed trait
GENETICAL TERMINOLOGIES:
• Genotype – genetic makeup of an individual (example: Nn or nn)
• Phenotype – observed characteristics (example: long or short neck)
REFERENCE LIST:
Campbell, J. & Recee, C. (2010). Biology: Genetics. (8th edition). Peason: Benjiam Publishers.
Mjnap. (11 months). geneticdiseasespresentation-130311073210-phpapp01.pptx http://s3.amazonaws.com/ppt-download/geneticdiseasespresentation-130311073210-phpapp01.pptx?response-content-disposition=attachment&Signature=xy7W%2BzyjqBXGmoN92xhDYiv98nY%3D&Expires=1394099263&AWSAccessKeyId=AKIAIW74DRRRQSO4NIKA. Accessed: 06/03/2014
SECBIO. (5months). genetics-130907092527-.pptxhttp://s3.amazonaws.com/ppt-download/genetics-130907092527-.pptx?response-content-disp. Accesed : 06/03/2014.
SPITZECA. (2011). geneticspresentationsuggestededits-110831055527-phpapp02 (1).pptxhttp://s3.amazonaws.com/ppt-download/geneticspresentationsuggestededits-110831055527-phpapp02.pptx?response-content-disposition=attachment&Signature=SUVNHZLSIXe6lQJp%2BjDafYz8HPE%3D&Expires=1394099134&AWSAccessKeyId=AKIAIW74DRRRQSO4NIKA. ACCESSED: 06/03/2014