BSCI 222 TOPIC 4

Environmental clues

Temperature, Chemical, maternal clues, social clues

Sequential hermaphroditism

Cues may induce hormonal changes that help an individual change from one sec to another

Haplo-diploid sex determination

sex determined by the individuals ploidy

Chromosomal sex determination

Sex determines by sex chromosomes

Genic sex determination

Sex determined by single gene on an autosomal chromosome

XY sex chromosomes if

Female has two of the same (XX)

Male has different (XY)

ZW sex chromosomes

Female has different (ZW)

Male has two of the same (ZZ)

Homogametic Sex

Produces gametes that have all the same sex chromosomes type

Heterogametic sex

Produces 50% gametes with one type of sex chromosome and 50% gametes with the other

XO sex determination

Sexes differ in ploidy for the sex chromosome only

Females XX (diploid for sex chromosome)

Males XO (haploid for sex chromosome)

SRY genes

Sec determining gene in humans

Sex-linked traits

Inheritance is affected when genes are located on the differentiated sex chromosomes (rather than autosomes)

Sex linked traits may be

X linked

Y linked

Z linked

W linked

Reciprocal cross

Switch which parent has which phenotype

Pedigree

A chart that shows familial relationships and inheritance of a specific phenotype of interest

Autosomal dominant phenotype

Phenotype never skips a generation.

Affected personal have at least one affect parent.

Phenotype appears with equal frequency in males and females

Approximately ½ 9; each generation is affected

Autosomal recessive phenotype

Phenotype tends to skip generations

Phenotype usually appears with equal frequency in males and females

Phenotype is more likely to appear among progeny of related individuals

X-linked recessive

Phenotype often skips a generation

Phenotype does not pass from father to son

Male passes his one allele to all daughter as carrier

Phenotype appears more in males than females

X linked dominant

Phenotype does not skip a generation

affected fathers pass their one allele on to all daughters but not sons

Affected mothers pass their allele to ½ of daughters and ½ ro the sons

Both males and females affected females tend to be affected more often

Y linked phenotype

Only males are affected

Phenotype is passed frm father to son if father is affected all sons will be

Phenotype does not skip generations

Sex linked traits- mitochondrial DNA

found in both sperm and egg

Inherited maternally

All progeny of mother inherit

Ends at sons