Today, we know that not all alleles behave quite as straightforwardly as in Mendel’s experiments. For example, in real life: Allele pairs may have a variety of dominance relationships (that is, one allele of the pair may not completely “hide” the other in the heterozygote). There are often many different alleles of a gene in a population.
In these cases, an organism's genotype, or set of alleles, still determines its phenotype, or observable features. However, a variety of alleles may interact with one another in different ways to specify phenotype. As a side note, we're probably lucky that Mendel's pea genes didn't show these complexities.
Chapter 1 Genetics: The Study of Biological Information Terms in this set (173) Allele one of two alternate forms of a gene that can have the same locus on homologous chromosomes and are responsible for alternative traits genotype the particular alleles at specified loci present in an organism phenotype
To find the number of alleles in a given population, you must look at all the phenotypes present. The phenotypes that represent the allele are often masked by dominant and recessive alleles working in conjunction. To analyze the allele frequency in a population, scientists use the Hardy-Weinberg (HW) equation.
The Hardy-Weinberg equation is used to predict genotype frequencies in a population. Predicted genotype frequencies are compared with actual frequencies.
Which of the following is NOT an assumption required for Hardy-Weinberg equilibrium? Explanation: Hardy-Weinberg states that for a population to be in equilibrium, it must not be experiencing migration, genetic drift, mutation, or selection. By this definition, population size cannot fluctuate.
Incomplete dominance occurs when neither trait is truly dominant over the other. This means that both traits can be expressed in the same regions, resulting a blending of two phenotypes. If a white and black dog produce a gray offspring, this is an example of incomplete dominance.
Hardy–Weinberg Equilibrium (HWE) is a null model of the relationship between allele and genotype frequencies, both within and between generations, under assumptions of no mutation, no migration, no selection, random mating, and infinite population size.
Which of the following is NOT a condition of the Hardy-Weinberg equilibrium? Mutations cannot occur in a population. Mating within a population must be random.
What is a possible explanation for why a population may not be in Hardy-Weinberg equilibrium? Evolution is occurring on a trait in the population. When we say "populations evolve, not individuals," what does this mean? Individuals cannot change their genetic makeup, but genotype frequencies in a population can change.
Incomplete dominance is a form of intermediate inheritance in which one allele for a specific trait is not completely expressed over its paired allele. This results in a third phenotype in which the expressed physical trait is a combination of the phenotypes of both alleles.
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.
Incomplete dominance is when the phenotypes of the two parents blend together to create a new phenotype for their offspring. An example is a white flower and a red flower producing pink flowers. Codominance is when the two parent phenotypes are expressed together in the offspring.
So, the correct answer is 'The population is small'
Assumption 1: No Genetic Drift This is known as genetic drift, and the Hardy-Weinberg assumes that it does not happen. In practical terms, a population at Hardy-Weinberg equilibrium has to be large enough that the frequency of an allele is not impacted by random events.
The 5 factors are – gene flow, mutation, genetic drift, genetic recombination and natural selection.
The 5 factors are – gene flow, mutation, genetic drift, genetic recombination and natural selection.
Factors that affect Hardy Weinberg equilibrium are gene migration, genetic drift, natural selection, mutation and genetic recombination. These factors change the allele frequencies in a population.
To know if a population is in Hardy-Weinberg Equilibrium scientists have to observe at least two generations. If the allele frequencies are the same for both generations then the population is in Hardy-Weinberg Equilibrium.
Reason: Gene flow can alter allele frequencies in the population. Which condition would disturb the Hardy-Weinberg equilibrium and cause the gene pool to change? The hurricane has caused a population bottleneck and a loss of genetic diversity.
To find the number of alleles in a given population, you must look at all the phenotypes present. The phenotypes that represent the allele are often masked by dominant and recessive alleles working in conjunction. To analyze the allele frequency in a population, scientists use the Hardy-Weinberg (HW) equation.
Allele frequency can change over time as evolution acts upon a population and the population adapts by increasing or decreasing the frequency of certain alleles. Calculating allele frequencies is a complex topic, which combines aspects of math and genetics. In general, all of the alleles in a population add up to 100%.
The white rabbits account for 16 of the 100 total rabbits. In a percentage, this is exactly 16%, or 0.16. This number is equivalent to q 2. Taking the square root, we find that the allele frequency of q (white) is 0.4, or 40%.
1. In a population of flowers, a certain allele is lethal to the plant if the plant is homozygous recessive for the genotype. A single recessive allele with a dominant allele, a heterozygote, will produce a totally health plant, indistinguishable from a homozygous dominant plant. A scientist fertilizes 100 seeds, of which only 75 sprout. The scientist thinks the plants that didn’t sprout all had the lethal homozygous recessive genotype. What is the allele frequency of the recessive allele in the population?
The term p 2 represents the frequency of the homozygous dominant genotype. The other term, q 2, represents the frequency of the homozygous recessive genotype.
The allele frequency is different from the phenotypic ratio in that it accounts for all alleles, even if they are recessive and are “hidden” within carrier organisms. The phenotypic ratio only describes the phenotypes, or actual physical features that are present within a population.
The allele frequency is the number of individual alleles of a certain type, divided by the total number of alleles of all types in a population. In simple terms, the allele frequency describes how common an allele is within a population.
T or F:Mendel's law of segregation states that two alleles for each trait unite in a specific manner during gamete formation and therefore give rise to predictable observable traits.
Chapter 1 Genetics: The Study of Biological Information
T or F:At fertilization, in the mating of dihybrids, four different kinds of eggs can combine with four different kinds of pollen, producing a total of sixteen different genotypes.
Inherited trait expressed only when the controlling gene is homozygous.
T or F:If you know the phenotype and the dominance relation of the alleles you can predict the genotype.
one allele is not completely dominant over the other allele
We could also consider the possibility that the homozygous parent possesses two recessive alleles. Here if the homozygous parent has two recessive alleles, then half of the offspring will exhibit the recessive trait with genotype bb. The other half will exhibit the dominant trait but with heterozygous genotype Bb.
In other words, there is a 100% probability that an offspring of such a pairing will exhibit the dominant phenotype.
If both parents are heterozygous for the trait in question, then they both have the same genotype consisting of one dominant and one recessive allele.
An individual with pairings of BB or Bb will both exhibit the dominant trait of brown eyes, even though the pairings of alleles are different. Here the specific pair of alleles are known as the genotype of the individual. The trait that is displayed is called the phenotype.
The Punnett square from this configuration is below. Here we see that there are three ways for an offspring to exhibit a dominant trait and one way for recessive. This means that there is a 75% probability that an offspring will have the dominant trait and a 25% probability that an offspring will have a recessive trait.
The trait that is displayed is called the phenotype. So for the phenotype of brown eyes, there are two genotypes. For the phenotype of blue eyes, there is a single genotype. The remaining terms to discuss pertain to the compositions of the genotypes. A genotype such as either BB or bb the alleles are identical.
Statistics and probability have many applications to science. One such connection between another discipline is in the field of genetics. Many aspects of genetics are really just applied probability. We will see how a table known as a Punnett square can be used to calculate the probabilities of offspring having particular genetic traits.
frequencies of alleles are more stable from generation to generation when the population is large, but populations will not stay 100% constant with their allele frequencies due to the forces of microevolution. Give hypothetical (or real) examples of a population bottleneck and the founder effect.
PHENOTYPES are the physical expression/characteristics of GENOTYPES - therefore, heritable differences in phenotypes must come from genetic differences.
In your own words, define/describe genetic drift. Change in allele frequencies due to random sampling of alleles. - ALL populations are influenced by genetic drift at ALL times. -allele frequencies of small populations are more likely to be significantly altered by genetic drift.
Movement of individuals OR gametes can affect the allele frequencies of populations. -gene flow is best defined as movement of alleles between populations -movement of a whole population to an area where there are no others is NOT gene flow. -formation of a new population is NOT gene flow.
Prokaryotes = genetic recombination, where genetic material of two organisms is combined, occurs in several ways, increasing variation. BOTH can experience mutations. Click again to see term 👆. Tap again to see term 👆. Explain why heritable differences in the phenotypes of organisms must be due to genetic differences.
Sexual selection increases the frequencies of traits that improve an individual's chances of getting a mate. - traits favored by sexual selection MUST increase attractiveness to opposite sex. - may DECREASE ability to survive. In one population of birds, females have very short tails and males have very long tails.
The cell cannot rid itself of the HIV genome because the integrase (enzyme) integrates the HIV DNA into the host cell, which means that the host cell and its chromosomes are permanently altered.
Hypothesis: If either parent mouse passes a dominant allele, then the offspring will have black fur.
B.Mice don't have large litters, so the sample size was not large enough.
Therefore, both parents pass the (b) allele to every offspring.
Scientists would make predictions based on observations of those traits, and then test out their ideas about the inheritance of a genetic trait by crossing the organisms in question and examining the offspring.
The traits that are passed from parents to offspring are determined by the combination of genes ( genotype) that are in the gametes. Which allele is passed on by a parent is a random event in nature. The probability of a particular event occurring is the fraction ...
A completed Punnett square gives the probable outcome of a given cross. In this case, the probability of each phenotype (green vs. yellow) is 50%. The probability of offspring with genotype Yy is 50%, as the probability of genotype yy. We can write these offspring probabilities as ratios to simplify our results:
Whenever two individuals that are heterozygous for both traits are involved in a Punnett square, we see four different phenotype groups with a typical 9:3:3:1 phenotype ratio.
If the mystery plant is a heterozygote (Yy) then you will see recessive phenotypes in the offspring. If the mystery plant is a homozygote (YY) then you will see all dominant phenotypes in the offspring. Monohybrid v. Dihybrid Crosses. So far, all of the Punnett square problems you have been solving have involved only one trait, ...
A testcross involves crossing the unknown organism with a an organism that is known to be homozygous recessive. If any of the offspring are homozygous recessive and show the recessive phenotype, then the unknown had to be heterozygous. Look below at the two possible outcomes of a testcross.
Each gamete (row or column) would have two letters, and each offspring box would have four letters. A cat that has a short tail ( Ss) and Brown fur ( Bb) can be crossed with another cat that has the same genotype (SsBb). To do this cross, a 16 box Punnett square must be used.
In this Punnett square, 2/4 (50%) of the offspring will have the genotype Aa. This will pres
1/4 (25%) of the offspring will have the genotype AA, which is homozygous for blonde hair.
First: we know that B = brown, and b = blue. We also know that heterozygous means having a combination of both the dominant and recessive alleles. The problem states that both parents are heterozygous for brown eyes, so they both must have a genotype of Bb. Here, the dominant B allele masks the recessive b allele, resulting in the parents having brown eyes.
The two genotypes on the side are the parents, and so from the Punnett Square above, we can see that the chance of having a blue eyed child is 25% , and a brown eyed child is 75%.
As the Punnett square shows, only 1 out of 4 possible phenotypes will be blue. So the probability of these parents having a child with blue eyes is 25% .
In the above Punnett square, both parents are heterozygous- they have one Allele for blonde hair and one allele for brown hair. Since blonde hair is dominant, they both have blonde hair.