DOMINANT AND RECESIVE TRAITSPresentation Transcript
DOMINANT AND RECESSIVE TRAITS
DOM I NA NC E T R A I T S : Dominance in genetics is a relationship between two alleles of a gene, in which one allele masks the phenotype (the expression that we can see in the outside) of another allele at the same genetics.
R E C E S S IV E T R A IT S : A recessive trait is a trait caused by a recessive gene, which means that someone must inherit two copies of the gene for the trait to manifest. When organisms such as humans reproduce, they produce young with a genetic inheritance from both parents, caused by the fusing of haploid sperm with haploid eggs to create a diploid organism.(In our case we have 46 chromosomes, 23 comes from each parent), so each chromosome contains a series of alleles or genes which code various information.
E X P L A N A T IO N : When someone is heterozygous, however, one of the alleles will remain inactive, and this allele represents a recessive trait. Gregor Mendel(considered the father od genetics beacuse of his experiments on the fields)did much of his work with peas. In the course of his research, he learned that purple was a dominant trait for flower color, meaning that a flower only had to inherit one purple gene to produce purple flowers. When someone is heterozygous for a trait, the difference between dominant and recessive traits becomes more important, because the dominant trait is the one which will manifest.
F O R E XA M P L E : When the alleles from both parents are the same(AAAA), someone is said to be homozygous at that allele. If a child inherits two different alleles, such as a gene for red hair(RR) and a gene for brown hair(BB), he or she is said to be heterozygous at that allele: When someone inherits the same allele twice,, that trait will manifest whether or not it is dominant. When someone is heterozygous, however, one of the alleles will remain inactive, and this allele represents a recessive trait.
E XA M P L E SIn the simplest case, where a gene exists in two allelic forms ( A and b), three combinations of genotypes(alleles) are possible: AA: Homozygotic dominant. Ab: Heterozygotic dominat. bb:HOmozygotic recessive. If AA and bb individuals (homozygotics) show different forms of the trait (phenotype), and Ab individuals (heterozygotics) show the same phenotype as AA individuals, then allele A is said to dominate or be dominant to or show dominance to allele b, and b is said to be recessive to A.
E XA M P L E S :1The language of genetics consists of symbols and rules for using these symbols.When thetrait that we are studying is dominant we use a capital letter to show its symbol. When werepresent the recessive trait from the same trait we put the same letter but not capitalized.EXAMPLE: If we have a tall pea plant dominat iver a short pea plant it will be represented like that: Dominan(tall): T Recessive(short): t2The following letters represent pairs of alleles.we have to indicate whether each pair is aheterozygote(hybrid) or homozygote(purebrid).Later we can indicate whether each pair woulddisplay a dominant or recessive phenotype DD:Homozygotic dominant Dd:Heterozygotic dominant ss:Hmozygotic recessive Rr: Heterozygotic dominant Tt:Heterozygotic dominant yy:Homozygotic recessive
S OURC ES :Ive got my information from these places:http://www.wisegeek.com/whatisarecessivetrait.htmhttp://en.wikipedia.org/wiki/Dominance_(genetics)My notebook and my own nowledge.