GENETICS Flashcards
What is genetics?
Genetics is the study of heredity - transmission of body features from parents to offspring - and the laws regarding such transmission.
Who is the father of genetics?
Gregor J Mendel
What are 2 modern applications of genetics?
- genetic engineering
- genetic councelling
What is genetic engineering?
It is a technique where the genetic constitution of an organism is altered by introducing new genes into its chromosomes
Define heredity
Heredity is the transmission of genetically based characteristics from parents to offspring
Define character
Any inheritable feature of an organism
Define trait
An alternative form of a character
What is a karyotype?
The arrangement of chromosomes on a chart based on their size and shape
How many chromosomes are present in one cell of a human?
46 chromosomes
What are homologous chromosomes?
A pair of corresponding chromosomes of the same shape and size, one obtained from each parent
What are autosomes?
Autosomes are chromosomes that determine general body features such as complexion, height, seed colour etc.
Humans have 22 pairs of autosomes
What are allosomes?
Allosomes - also called sex chromosomes - are the chromosomes that determine the sex of an organism.
Each human has 1 pair of allosomes in a cell
How is the sex of an organism determined?
If the egg bearing X chromosome is fused by X bearing sperm - XX - daughter
If the egg bearing X chromosome is fused by Y bearing sperm - XY - son
Who coined the term ‘gene’?
Geneticist Wilhelm Johanssen
What is genome?
The full complement of DNA including all genes and intergenic regions of an organism
What is an allele?
Alleles are alternative forms of a gene that occupy the same position on homologous chromosomes affective the same characteristic in different ways
What is a dominant allele?
The kind of allele that expresses itself regardless of the presence of another allele
What is a recessive allele?
The kind of allele that expresses itself only in the presence of the same recessive allele and gets suppressed in the presence of a dominant allele
What is the dominant and recessive allele for the height of a garden pea?
Dominant - tall
Recessive - dwarf
What is genotype?
The set of genes present in the cells of an organism
What is phenotype?
The observable characteristics of an organism that are genetically controlled
What does RR mean?
Homozygous dominant
What does Rr mean?
Heterozygous dominant
What does rr mean
Homozygous recessive
What is sex LinkedIn inheritance?
The appearance of a trait which is due to the presence of an allele on the X chromosome or on the Y chromosome
What are X linked disorders?
The disorders such as haemophilia and colour blindness that occurs due to the presence of a recessive gene on the X chromosome
What is haemophilia?
It is a genetic disorder in which sufferers are at a risk of bleeding to death as blood fails to clot in them
What is the scientific name of the garden pea?
Pisum sativum
Why did Mendel choose the garden pea for his experiments?
- The garden pea self pollinated
- they were available in pure forms that bred true
- A lot of generations could be obtained and studied in a short period of time
- many varieties with alternative forms were available
What does F1, F2 and F3 mean?
F1 - first fillial gen - first generation of offspring
F2 - second fillial gen - second generation of offspring
F3 - third fillial gen - third generation of offspring
What is the genotypic and phenotypic ratio of the monohybrid cross in F2 generation if the gametes are
(aa) & (AA)?
genotype - 1:2:1
phenotype - 3:1
What is the phenotypic ratio of the dihybrid cross in F2 generation if the gametes are
(aa) & (AA)?
9:3:3:1
What are Mendel’s 3 laws of inheritance?
- law of dominance
- law of segregation
- law of independent assortment
What is the law of dominance?
Out of a pair of contrasting characters, 1 expresses itself while the other remains suppressed.
What is the law of segregation?
2 members of a pair of factors separate during formation of gametes
What is the law of independent assortment?
When there are two pairs of characters, the distribution of an allele of one character into the gametes is independent of the distribution of other alleles of the other character.
What are the applications of Mendel’s laws?
- production of better breeds
- information about new combinations in the progeny of hybrids
- hybridisation to produce new types of plants with new combinations of characters
Define mutation.
A sudden change in one or more genes, or in the number or structure of chromosomes
How did the atomic explosion of Hiroshima, Nagasaki in Japan cause mutations?
The radioactive radiations caused the altering of gene structures which caused deformities in the bodies of plants and animals.
What is sickle cell anaemia?
A blood disease caused by a genetic mutation that causes a change in DNA resulting in the production of sickle shaped RBCs
