In this presentation you will see: how traits can be inherited dominant and recessive traits

Heredity Traits 2 • In this presentation you will see: • how traits can be inherited • dominant and recessive traits • how traits in offspring can be predicted and visually represented Next >

Introduction The characteristics of living things vary, and heredity traits are passed on through generations. This is inheritance. Heredity traits can be predicted in offspring when the genetic make-up of the parents are known. Next >

Variation Variation exists within species. This variation is partly due to the genes that the individuals possess. Alleles are different forms of the same gene. For example, there are different alleles for eye color or hair color. The allele combinations that you possess are responsible for your unique mix of characteristics. Next >

Alleles Genes and Inheritance Living things inherit their alleles from their biological parents. Genes normally work in pairs. One copy of each gene comes from each biological parent. Next >

Genes and Inheritance The alleles an organism inherits may be the same … … but they will often be different. Due to the way that genes are inherited, the probability of offspring inheriting certain alleles and expressing certain traits, can easily be predicted if the parents’ alleles are known. Next >

Question 1 "Living things inherit their genes from their biological parents." Is this statement true or false? Answer True or False. Next >

Question 1 "Living things inherit their genes from their biological parents." Is this statement true or false? Answer True or False. True Next >

Question 2 Can living things have different alleles for the same gene? Answer Yes or No. Next >

Question 2 Can living things have different alleles for the same gene? Answer Yes or No. Yes Next >

Dominant allele Recessive allele Dominant and Recessive Alleles In a gene pair, one allele can be dominant over another. This means that the effects of some alleles mask the effects of others. The gene that controls the shape of your little finger has two alleles. Next >

Dominant allele Recessive alleles F f F F Dominant and Recessive Alleles People who have a straight little finger, that does not bend toward the other fingers, possess two recessive alleles (ff). People who have a little finger that does bend toward the other fingers, either possess two dominant alleles (FF), or one dominant, and one recessive, allele (Ff). f f Next >

Recessive allele Dominant allele Dominant and Recessive Alleles The effect of the F allele masks the effect of the f allele. The F allele is dominant, the f allele is recessive. Dominant and recessive alleles are usually shown using upper and lower case letters. Upper case letters represent a dominant allele, lower case letters represent a recessive allele. Next >

Alleles f f F F F f Homozygous and Heterozygous Individuals that have two of the same alleles for a gene are said to be homozygous. Individuals that have two different alleles for the same gene are said to be heterozygous. Next >

Question 3 If an allele is recessive, ... A) ...it can mask the effect of dominant alleles. B) ...it can be masked by the effects of dominant alleles. C) ...it is normally shown by using upper case letters. D) ...its effects can be seen in a heterozygous organism. Next >

Genotype and Phenotype The alleles that an individual possesses within its DNA are known as its genotype. FF = Genotype The visible characteristics that result from the individual’s alleles is known as its phenotype. The inheritance of simple genetic traits that involve two different alleles of the same gene is known as monohybrid inheritance. Bent finger = Phenotype Next >

Monohybrid Inheritance Monohybrid inheritance is the inheritance of a single characteristic that is controlled by two alleles of the same gene; one dominant allele and one recessive allele. Parent A F f f Ff ff Parent B f Ff ff The way that alleles can be passed down from parents to offspring can be shown by using Punnett squares. Next >

Punnett Squares A Punnett square demonstrates all the possible genotypes that can result from the random fusion of parent gametes. Parent A F f The alleles within the gametes of one parent are written across the top of the square. f Parent B f The alleles within the gametes of the other parent are written down the side of the square. Next >

50 % 50 % Punnett Squares The possible product variation after fusion of the gametes are written in the appropriate boxes. This shows the offspring genotypes that are possible. Parent A Ff ff F f Ff ff f Parent B f When the square is complete, the proportion of the possible offspring genotypes (and phenotypes) can be estimated. Next >

FF ff FF FF ff ff f f f f F F F F Monohybrid Inheritance The way that alleles can be passed from parents to their offspring can be shown in a number of ways. One way is the monohybrid cross. We will look at the crossing of a homozygous male whose finger bends (FF), with a homozygous female whose finger does not bend (ff). Next >

f F Monohybrid Inheritance Cells divide in the female’s ovaries and the male’s testes to produce gametes (cells that only have one copy of each gene). Bent finger Straight finger Parent phenotypes Parent genotypes FF ff Gamete genotypes The male is FF homozygous and will produce gametes that all have the F allele. The female is ff homozygous and will produce gametes that all have the f allele. Next >

f F Male gametes Offspring genotype and phenotype: F Ff Bent finger Female gametes f Monohybrid Inheritance When these homozygous individuals mate together, their gametes fuse to form zygotes. Bent finger Straight finger Parent phenotypes Every zygote has two copies of each gene, one from each parent, so the zygotes from this pair will all have the genotype Ff. Parent genotypes FF ff Gamete genotypes Since F is dominant, every zygote will have the bent finger phenotype. Next >

Parent phenotypes Bent finger Bent finger Ff Ff Parent genotypes Gamete genotypes and and f F F f Monohybrid Inheritance In this example, we can see how genotypes can be inherited by offspring when both parents are heterozygous (Ff). (Allele F is dominant to allele f) Half of each parent’s gametes will have F alleles and half will have f alleles. Next >

Parent phenotypes Bent finger Bent finger Ff Ff Parent genotypes Gamete genotypes and and f F F f Monohybrid Inheritance There is equal chance of a gamete with the F allele joining to a gamete with an F or an f allele from the other parent. (Allele F is dominant to allele f) Next >

Parent phenotypes Bent finger Bent finger Ff Ff Parent genotypes Gamete genotypes and and f F F f Male gametes Offspring genotypes and phenotypes: f F F Female gametes f FF Bent finger Ff Bent finger Ff Bent finger ff Straight finger Monohybrid Inheritance (Allele F is dominant to allele f) There is only a 25% chance that an offspring will have the straight finger phenotype. Next >

Male gametes H Hh Wavy hair h Femalegametes Male gametes h H Hh Wavy hair HH Straight hair H Female gametes hh Curly hair Hh Wavy hair h Monohybrid Inheritance Not all alleles are either dominant or recessive. Some alleles are codominant, so if an organism is heterozygous, both alleles affect the phenotype of the organism. An example is hair type. Here, the genotype HHresults in straight hair, hh gives curly hair, but a genotype of Hh gives wavy hair; an equal expression of both alleles. Next >

Question 4 Allele B is dominant over allele b. If an organism is heterozygous for these alleles, will the dominant allele reflect in the phenotype? Answer Yes or No. Next >

Question 4 Allele B is dominant over allele b. If an organism is heterozygous for these alleles, will the dominant allele reflect in the phenotype? Answer Yes or No. Yes Next >

Parent A T t T TT Tt Parent B t Tt X Question 5 This image shows an incomplete Punnett square for a cross concerning the tongue-rolling allele. Which of the following options shows the correct offspring genotype for the square labeled X? A) TT T = dominant t = recessive B) Tt C) tt D) None of these Next >

Question 6 Which of the following will a Punnett square show? A) The probabilities of the different genotypes of offspring B) The different genotypes of offspring C) The probabilities of the different phenotypes of offspring D) All of the above Next >

Summary In this presentation you have seen: • dominant and recessive alleles and traits • how genetic traits can be inherited • how heredity traits in offspring can be predicted and visually represented End >

In this presentation you will see: how traits can be inherited dominant and recessive traits