GENETICS AND INHERITANCE TELEMATICS 5 APRIL 2016

TERMINOLOGY: ALLELES version for yellow petals version for red petals FEMALE PARENT MALE PARENT Each chromosome may have a different version of a gene.

If the alleles in a matching pair are the same, they are called homozygous alleles. allele for yellow petals allele for yellow petals allele for red petals allele for red petals What colour are the flowers with these homozygous pairs of alleles? (Click twice on each bud to reveal the flower; click again to close them.)

If the alleles in a matching pair are different, they are called heterozygous alleles. Which characteristic is expressed if alleles are different? allele for yellow petals allele for red petals Some alleles are dominant to other forms of a gene and will always be expressed IN THE PHENOTYPE Which is the dominant allele in this heterozygous pair? Which is the recessive allele in this heterozygous pair? (Click twice on the bud to reveal the flower; click again to close it.)

What colour are flowers with the genotype Rr A dominant allele is always a capital letter. A recessive allele is always the corresponding small letter. allele for red petals R allele for yellow petals r = =

GENETIC CROSSES

APPEARANCE OF BOTH PARENTS THE TWO ALLELES OF BOTH PARENTS GAMETE GENOTYPE F1 GENOTYPE F1 GENOTYPE F1 GENOTYPE F1

On page 9… WHAT MUST YOU LOOK FOR 1 ST ? 1.The characteristic……. 2.identify the dominant and recessive trait 3.To determine the genotypes……is the person HOMOZYGOUS or HETEROZYGOUS for the trait

Tongue-roller is DOMINANT = T That means…non-roller is recessive = t To be a roller: TT or Tt …….WHY? The ONLY way to be a non-roller is to be HOMOZYGOUS RECESSIVE = tt

T t t t Tt tt

BB (homozygous dominant) x bb (Homozygous recessive) BB b b Bb

Bb (heterozygous) x Bb (Heterozygous) B b B b BB Bbbb Bb GENOTYPE: 1 BB: 2Bb:1bb PHENOTYPE: 3:1

Bb (heterozygous) x bb (homozygous recessive) Bb b b Bb bb 50%:50% OR 1:1

REMEMBER: ……………………………. With INCOMPLETE DOMINANCE and CO-DOMINANCE……… We represent the genotypes by using only CAPITAL LETTERS ………

WW RW RR P1 Generation F1 Generation

18 Co-dominance Both the alleles can be expressed Eg. Red cows crossed with white bull will generate Roan calves. Might seem to support blending theory. But F 2 generation demonstrate Mendalian genetics (1:2:1)

The alleles for haemophilia are indicated as superscripts on the sex chromosomes, X H Y (normal male), X h Y (male with haemophilia).

SEX-LINKED INHERITANCE

A normal father and heterozygous normal mother have children. Represent a genetic cross to determine the possible genotypes and phenotypes of their children. NORMAL FATHER: X H Y HETEROZYGOUS (NORMAL) MOTHER: X H X h DETERMINE THE GENOTYPES

XHXH XhXh XHXH Y XHXHXHXH XHXhXHXh XHYXHY XhYXhY

Telematics Life Sciences XhYXhY XhYXhY XhYXhY XHYXHYXHYXHY XHYXHY XHXhXHXh XHXhXHXh XHXHXHXH XHXhXHXh XHXHXHXH XHXhXHXh

In pea plants, the allele for tallness (T) is dominant and the allele for shortness (t) is recessive. The allele for purple flowers is dominant (P) and the allele for white flowers is recessive (p). Two plants, heterozygous for both tallness and purple flowers, were crossed.

TPTp tP tp

TP Tp tP tp TtPp x TtPp TPTptPtp TPTTPPTTPpTtPPTtPp TpTTPpTTppTtPpTtpp tPTtPPTtPpttPPttPp tpTtPpTtppttPpttpp

A rare form of rickets in humans is caused by a sex- linked dominant allele ( R ) which is carried on the X- chromosome. An affected female, whose father was unaffected, married an unaffected male.