Genetics

How do dominant and recessive alleles differ?

-Dominant alleles differ in a way because they are more likely to be carried on and passed down to their offspring -Recessive alleles are less likely to be passed down from their parents because they are less common A dominant allele produces a dominant phenotype in individuals who have one copy of the allele, which can come from just one parent. For a recessive allele to produce a recessive phenotype, the individual must have two copies, one from each parent.

What is the purpose of using a punnett square? Do punnett squares determine the genotypes for 4 children or do they determine the probability of having child with a certain genotype? Does the genotype of the 1st born child affect the genotypes of the children after him? How do changes in DNA impact an organism's phenotype?

-Helps to predict the variations and probabilities that can come from cross breeding. -allows you to determine the expected percentages of different genotypes in the offspring of two parents. -It determines on which sperm cell decides to fertilize which egg. It doesn't affect the children after them -Any change in the gene sequence can change the phenotype expressed in inherited alleles.

Explain Mendel's law of segregation and law of independent assortment. When does allele segregation and independent assortment occur? Do genes that assort independently influence each others inheritance? Explain how the location of genes on different vs the same chromosome impacts sorting into gametes.

-The law of segregation states that every individual possesses two alleles and only one allele is passed on to the offspring. The law of independent assortment states that the inheritance of one pair of genes is independent of inheritance of another pair. -During the process of meiosis, when gametes are formed, the allele pairs segregate, i.e. they separate. For the determination of a Mendelian trait, two alleles are involved — one is recessive and the other is dominant. -What is the law of independent assortment? Mendel's law of independent assortment states that the alleles of two (or more) different genes get sorted into gametes independently of one another. In other words, the allele a gamete receives for one gene does not influence the allele received for another gene. -Alleles of genes close to each other on the same chromosome don't have an equal chance of being sorted into different gametes. Through crossing over, linked alleles may end up in different gametes, but at a lower rate than if they were on different chromosomes (or far apart on the same chromosome).

How many alleles for each trait do gametes have?

1 (gametes are haploid and only carry ½ of the diploid number of chromosomes). Thus, each gamete receives single allele of a gene. Owing to their haploid status, gametes carry one complete set of chromosomes which in turn carry the single allele for each gene.

Be able to identify if a trait on a given pedigree is recessive, dominant, or sex-linked

1.Determine whether the trait is dominant or recessive. If the trait is dominant, one of the parents must have the trait. Dominant traits will not skip a generation. If the trait is recessive, neither parent is required to have the trait since they can be heterozygous. 2.Determine if the chart shows an autosomal or sex-linked (usually X-linked) trait. For example, in X-linked recessive traits, males are much more commonly affected than females. In autosomal traits, both males and females are equally likely to be affected (usually in equal proportions).

Explain the relationship between alleles and genes

An allele is a different variation of a gene. One gene usually has 2 alleles but can have more than 2. Alleles are different versions of genes.

What is the difference between autosomes and sex chromosomes?

Autosomes: Autosomes determine somatic traits, males and females contain the same copy of autosomes, labeled with numbers from 1 to 22, most chromosomes within a genome are autosomes, 22 pairs of autosomes are homologous in humans, position of the centromere is identical. Sex chromosomes: Sex chromosomes determine the gender, different in males and females by their size, form, and behavior, labeled with letters as xy,zw,xo,zo, Few chromosomes within a genome are sex chromosomes, female sex chromosomes (xx) are homologous; male sex chromosomes (xy) are non-homologous, position of the centromere is not identical.

Describe how inheritance patterns involving multiple alleles (specifically blood types)

Blood types-Blood type is inherited through a codominant inheritance pattern; neither allele masks the other. Instead, people who get two different alleles, called heterozygotes, express both alleles equally. In blood type, A and B alleles are codominant. -There are traits in humans and other organisms that have three or more different types of alleles (genes). When a trait has three or more distinct alleles, we refer to it as having multiple alleles inheritance. The human ABO blood type alleles/trait is an example of a trait with multiple alleles.

Be able to draw and analyze a given pedigree to identify genotypes and phenotypes

By analyzing a pedigree, we can determine genotypes, identify phenotypes, and predict how a trait will be passed on in the future. The information from a pedigree makes it possible to determine how certain alleles are inherited: whether they are dominant, recessive, autosomal, or sex-linked.

Describe how alleles interact in incomplete dominance and codominance

Codominance and Incomplete dominance are two types of genetic inheritance. Codominance essentially means that no allele can block or mask the expression of the other allele. On the other hand, incomplete dominance is a condition in which a dominant allele does not completely mask the effects of a recessive allele.

What genotypes express the dominant and recessive phenotypes?

Dominant-AA,Aa Recessive-aa

Be able to explain how the environment can affect gene expression

Gene expression can be altered by environmental factors such as food, drugs or exposure to toxins

Explain why most sex-linked disorders are more common in males

In humans, the term often refers to traits or disorders influenced by genes on the X chromosome, as it contains many more genes than the smaller Y chromosome. Males, who have only a single copy of the X chromosome, are more likely to be affected by a sex-linked disorder than females, who have two copies.

Explain how polygenic inheritance can result in a range of phenotypes

In polygenic inheritance, each allele has a cumulative or additive effect on the phenotype thus generating continuous variation, e.g. skin pigmentation, height, etc.

How many alleles for each trait does a person have? Where do they come from?

Individuals inherit two versions of each gene, known as alleles, from each parent. In the case of a recessive trait, the alleles of the trait-causing gene are the same, and both (recessive) alleles must be present to express the trait. A recessive allele does not produce a trait at all when only one copy is present.

Explain how sex-linked genes produce different inheritance patterns in males and females

Males, who have only a single copy of the X chromosome, are more likely to be affected by a sex-linked disorder than females, who have two copies. In females, the presence of a second, non-mutated copy may cause different, milder, or no symptoms of a sex-linked disorder.

Be able to describe the difference between the types of chromosomal rearrangements

The four types of chromosomal changes are deletions, inversions, duplications, and translocations.

Be able to interpret a karyotype

This notation includes the total number of chromosomes, the sex chromosomes, and any extra or missing autosomal chromosomes. For example, 47, XY, +18 indicates that the patient has 47 chromosomes, is a male, and has an extra autosomal chromosome 18.

How can you use a testcross to determine the genotype of an unknown organism with the dominant phenotype?

To do a testcross, cross the phenotypically dominant organism and an unknown genotype with a recessive organism to determine the genotype of the dominant organism. If any progeny shows the recessive trait, the test organism must have been heterozygous.

Why are certain blood types called universal donors or recipients Explain how the Rh factor can affect pregnancies Be able to explain what creates different blood types and identify what blood types a person can accept or donate based on their blood type

Universal donors-blood group type O negative blood is the variety of blood that has the lowest risk of causing serious reactions for most people who receive it. Because of this, it's sometimes called the universal blood donor type. Recipients- A+ and it matches with A+, A-, O+, O- A- matches with A-, O- B+ matches with B+, B-, O+, O- B- matches with B-,O- -Blood types are determined by the presence or absence of certain antigens - substances that can trigger an immune response if they are foreign to the body. -Group AB can donate to other AB's but can receive from all others. Group B can donate red blood cells to B's and AB's. Group A can donate red blood cells to A's and AB's. Group O can donate red blood cells to anybody.

Which sex chromosome contains more genes? X or Y?

X

Does X chromosome have the same genes as the Y chromosome?

X chromosome (females have two of them, while males have one) is five times larger than the Y chromosome, and has 10 times the number of genes. That means it carries more traits — and diseases — than the Y chromosome. The X and the Y chromosomes do not have the same number of genes. The Y chromosome contains much fewer genes than the X chromosome. The Y chromosome only contains about 50 or so genes, whereas the X chromosome has more than 700 genes.

Can 2 organisms have the same phenotype but different genotypes?

yes, two different genotypes can result in the same phenotype. Remember, the recessive phenotype will be expressed only when the dominant allele is absent, or when an individual is homozygous recessive (tt)