No crossing over occurs. What combination s of chromosomes are possible in daughter cells following mitosis? What combination s of chromosomes are possible in haploid cells following both divisions of meiosis?
Males have one X and one Y-chromosome while females have two X-chromosomes. Due to the differences between the X and Y-chromosomes, the number and type of genes inherited by an individual depends on its sex.
The genes present on the X and Y-chromosomes are called sex-linked genes. Sex-linked genes and their related traits are further distinguished as either X-linked or Y-linked depending on which chromosome they are located. With both an X and a Y-chromosome, males inherit both X and Y-linked traits, while females only inherit X-linked traits.
Females get two copies of X-linked genes, so they demonstrate the more typical dominant-recessive expression patterns of non-sex linked traits. These distinctions cause expression patterns of sex-linked traits to differ between male and female offspring. Since the X-chromosome is bigger and contains more genes than the Y-chromosome, most sex-linked traits are X-linked traits.
Wild-type fruit flies have dark red eyes, but there are recessive alleles of this eye color gene called the white gene that cause individuals to have white eyes. As recessive trait, the white eye phenotype is masked by the presence of a wild-type red encoding allele. If the white gene were on an autosome, it would exhibit classical Mendelian inheritance patterns.
However, the gene is on the X-chromosome, making it an excellent illustration of sex-linked inheritance patterns. Select one male and one female individual for the P1 generation and click 'begin' to explore eye color inheritance patterns in fruit flies: Embed this illustration Copy the following iframe code and paste it where you want the illustration to appear: In females, the presence of a dominant red encoding allele XW will produce red eyes even if the individual in heterozygous for the white allele.
Females can be Homozygous dominant for the red encoding allele - genotype: Heterozygous - genotype XWXw; phenotype: Homozygous recessive with two white encoding alleles - genotype XwXw; phenotype white eyes. With only one copy of the X-chromosome, all males are hemizygous for this gene.
They have only two options: Hemizygous dominant - genotype: Reciprocal crosses involve crossing true breeding red and white-eyed individuals. Two reciprocal crosses can be performed: Performing the first reciprocal cross: However, with an X-linked gene, the reason for red eyes differs between males and females.
All of the female offspring are heterozygous receiving an X-chromosome with a red allele from their mother and an X-chromosome with the white allele from their father. The presence of the red allele masks the presence of the white allele. Male offsprings only have one X-chromosome which they received from their female parent.
In this reciprocal cross that allele has encode for red eyes.
So, females are red-eyed because the presence of the recessive copy is masked. Males are red-eyed because they only have one copy of the gene and that copy is for the red allele.
The differences between the sexes become more apparent when the red-eyed F1 male and red-eyed F1 females are crossed. The results of this cross produce a 3: No females have white eyes because they received one of their X-chromosomes from their hemizygous dominant, red-eyed father.
The male offspring all received their single X-chromosome from the heterozygous female parent, so half received a red allele, and half received a white allele.The Punnett square is a square diagram that is used to predict the genotypes of a particular cross or breeding experiment.
It is named after Reginald C. Punnett, who devised the approach. The diagram is used by biologists to determine the probability of an offspring having a particular genotype. Pedigree Analysis Using Punett Squares Essay Name: Megan Jackson Date: November 20, Graded Assignment Lab Report You may wish to construct the Punnett squares on scratch paper first before you fill in the Punnett squares on the Lab Report.
In both family studies, individuals with tongue-rolling parents are much more likely to be tongue-rollers than individuals with non-rolling parents. It is difficult to imagine how the common family environment could influence tongue-rolling, so this resemblance between relatives suggests that there is a large genetic influence on tongue-rolling.
Punnett Square Practice Problems. A plant species has two alleles for flower color: Red (R) and White (r). The Red (R) allele exhibits complete dominance. 2 squares = 50% probability 3 squares = 75% probability If the same genetype appears in all 4 boxes, % of the offspring will have that genotype.
Mary B. Biology Activities. An interactive way to teach punett squares using guinea pigs. students determine genotypes and then cut and paste correct phenotypes- Great for viisual learning students!
ScienceISfun. TpT Science Lessons. Introduction to Biology. Pedigree Analysis Activity Pedigree charts are often constructed to show the inheritance of genetic conditions within a family. Such charts are a great help in determining whether a phenotype is controlled by a dominant, recessive or sex-linked allele.