Genetics Flashcards
Genetics definition
The study of the inheritance of characteristics
Heredity def.
The passing on of features and characteristics from parents to offspring
Species definition
A group of organisms capable of interbreeding and producing fertile offspring
Variation definition
Variation means there are differences between members of the same species
Acquired characteristics
Characteristics developed/learned during life
Eg. Learning to sing, play rugby etc.
Inherited characteristics
Characteristics controlled by gene inherited from parents
Eg. Hair, eyes etc.
Name of bundle of chromosomes
Chromatin
Chromosomes
Thread like structure.
Found in nucleus in pairs
Made up of DNA (genetic info) and protein (holds DNA in place)
Genes arranges along the DNA on the chromosomes
The two types of cells
Sex cells- reproductive cells capable of fertilisation.
Eg. Sperm and egg
Somatic cells- any call except reproductive cells.
Eg. Cheek cells
Chromosome numbers in cells
Somatic: 46 chromosomes- 23 pairs
Sex cells: 23 chromosomes.
Types of chromosomes
Autosomes: non sex determining chromosomes, determines characteristics, 22 pairs
Sex chromosome: determines sex of individual. 2 sex chromosomes (X and Y)
Males: XY
Females: XX
Number of types of chromosomes in different cells
Somatic cells: 44 Autosomes, 2 sex
Sex cells: 22 Autosomes, 1 sex
Meiosis in testes to form sperm
Determines the sex of the individual.
Cells in testes divide by meiosis to produce sperm
X and Y go into different cells
1/2 sperm carry X and half carry Y
All eggs have X
Whichever sperm fuses with egg determines sex.
Sex determination
4 weeks after fertilisation, embryo that contains Y chromosome develops testes ( primary male sex organ). Testes secrete testosterone hormone. Testosterone signals to other cells to develop in male pattern
Gene definition
A gene is a section of DNA found on the chromosome that codes information for the making of specific protein.
Role of genes
Unit of inheritance
Controls the characteristics of an organism
Not everyone has the same version of those genes
More than one type of gene for hair colour
Characteristic definition
Influenced by
The features/ traits that an individual displays
Influenced by genes and environment
Gene expression definition
The way in which information on a gene is coded to make a protein.
Junk DNA
DNA that doesn’t code for any protein.
Found in between genes and on the gene
DNA
Name
Where
Types
Name: Deoxyribonucleic acid
Where: nucleus, mitochondria, chloroplast. None in cytoplasm or ribosome
Types: Nuclear DNA- in nucleus, inherited from both parents
Non Nuclear DNA - found in mito and chloroplast, inherited from mother only
Father of genetics
Gregor Mendel
Genetic crosses definition
Study of how characteristics are inherited.
Each characteristic is controlled by a pair of alleles present in cell
Gamete
A sex cell capable of fusion
Egg and sperm
Allele
Alternative form of gene
Eg. C, c, D, d
Locus
Location of gene on chromosome
Genotype
Genetic makeup of an organism Letters Female genotype: XX Male genotype: XY Other: Cc, GG, yy
Phenotype
Physical makeup of an organism
Eg. Blue eyes, brown hair, female etc.
Homozygous
Condition in a cell where the alleles present are the same
Eg. BB, bb, XX
Heterozygous
Condition in cell where the allele present are different
Eg. Bb, XY
Recessive allele
The allele that is not expressed in the phenotype of the individual. Eg. X is recessive in XY genotype.
Dominant allele
The allele that is expressed in the phenotype of the heterozygous condition.
Eg. Y is dominant in XY pairing
Incomplete dominance
Neither allele is expressed in the phenotype of the heterozygous condition, both are expressed together.
Eg. Roan in cattle colour where neither red or white display dominance.
Progeny/ F1 generation
Offspring produced
F2 generation
Offspring produced as a result of F1 crossing with another F1
Linkage
Genes that are located on the same chromosome
Sex linkage
The characteristic is controlled by a gene on the X chromosome
Monohybrid crosses
Study of inheritance of one characteristic
Eg. Eye colour
Dihybrid crosses
Study of inheritance of two characteristics
Eg. Hair colour and eye colour
Steps of a cross
Key Parents Gametes F1 generation Phenotype
Law of segregation
States that characteristics are controlled by a pair of alleles, which separate at gamete formation, with one allele in each gamete
Law of independent assortment
States that at gamete formation, either pair of alleles can combine with either allele of another pair of alleles.
Eg. Parent:GgLl
Gametes: GL Gl gL gl
Either g can combine with either l
Linkage crosses
Linked alleles must go in the same gamete
Significance of linkage
Less variety in progeny produced
Sex linkage crosses
Draw out!
Y never has another letter in the gamete. Trait carried by X chromosome
Always Y-
What characteristics are controlled by sex linkage
Colour blindness Haemophilia Albinism Male pattern baldness Muscular dystrophy Eye colour in fruit flies
Difference in male and females in sex linkage
Males can be either a sufferer or normal. Because no allele present on Y chromosome
Females can be sufferers, carriers or normal. Because X chromosome carries allele
