Fundamentals of genetics

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