LC Biology- Genetic crosses and Heredity

Gamete

haploid cells (sex cells)

What is the role of gametes in sexual reproduction?

Gametes transmit genes from one generation to another in sexual reproduction.

Fertilisation

The union of 2 gametes to form a single cell called a zygote(diploid)

Alleles

Forms of all the same gene

Locus

The locus of a gene is it’s location to the chromosome

Dominant

Means the allele that prevents the recessive allele from being expressed

Recessive

Means the allele is prevented from being expressed by dominant allele

Homozygous

Means 2 identical alleles (BB or bb)

Heterozygous

Means the alleles that are different (Bb)

What is a punnett square

A grid used to show the ratio of genotypes of progeny in a genetic cross

Incomplete dominance

When neither allele is dominant or recessive with respect to each other

Who was Gregor Mendel

“Father of genetics” came up with 2 basic laws of inheritance

Law of segregation

• inherited characteristics are controlled by a pair of alleles

• These allele will segregate from each other at gamete formation with only 1 pair being found in each gamete

What is a pedigree?

A diagram showing the genetic history of a group of related individuals

In sex determination how do humans differ from birds, butterflies and moths?

In these animals sex determination is determined by females (xy) and males (xx)

Mono hybrid cross

Involves study of one characteristics

Dihybrid cross

Involves study of 2 characteristics

Law of independent assortment

• When gametes are formed

• Either pair of alleles are equally likely to combine with either pair of alleles in the other gamete.

Linkage

Means that genes are located on the same chromosome.

• does NOT follow mendels 2nd law of independent assortment

Sex linkage

That a characteristic is controlled by a gene on a sex chromosome (x), also called x linked

Common sex linked traits

• colour blindness (male)

• Haemophilia

  All controlled by genes of alleles

Where else in the cell outside the nucleus is DNA found?

Non-nuclear DNA is found in chlorophlasts and mitochondria, ONLY passed from female

Genotype

The genetic make up of an organism

Phenotype

The physical appearance of an organism