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GENETICS
Exam 2-Mod 4-7
| Question | Answer |
|---|---|
| The phenotypic ratio expected from a dihybrid cross involving complete dominance is | 9:3:3:1 |
| EE and Ee are genotypes for brachydactyly (short fingers) and ee is the genotype for normal finger length. If a man and woman both have the genotype Ee, then what is the probability that their child will have normal fingers? | 1/4 |
| Some genetic diseases may be treated by providing a missing enzyme or protein. T or F | True |
| In the context of Mendel's experiments, one trait that masks another is ______. | dominant |
| In a Punnett square where are the gametes listed? | Along the top and the left side of the square |
| What are alleles? | alternate forms of a gene |
| Which of these compares the protein-encoding DNA sequences of the genomes of the members of a family? | Family exome analysis |
| A ____ in genetics differs from a family tree in genealogy in that it indicates diseases or traits as well as relationships and ancestry. It may also indicate molecular data and test results. | pedigree |
| DNA in the mitochondria | does not crossover and mutates faster than DNA in the nucleus |
| What is the genotype for type O blood | ii |
| What is the genotype for type A blood | IAIA or IAi |
| What is the genotype for type AB blood | IAIB |
| What is the genotype for type B blood | IBIB or IBi |
| The same phenotype may result from different genotypes due to | genetic heterogeneity |
| In humans, mitochondrial DNA typically exhibits | maternal inheritance |
| A phenotype is variably expressive if symptoms vary in intensity among different people. T or F | True |
| One person with polydactyly might have an extra digit on both hands and a foot, but another person might have just 1 extra fingertip. The SPECIFIC concept is best described by the fact that polydactyly is | variably expressive |
| _____ refers to the all or none expression of a genotype of a single gene. | penetrance |
| When a single gene loco has more than 2 possible alleles, this is called ______. | multiple alleles |
| Identify the different ways in which mitochondrial DNA provides a powerful forensic tool. | -by supporting or challenging historical records -by identifying war dead -by linking suspects to crime |
| Imprinting disorders illustrate _________ | epigenetic |
| x-linked inheritance | refers to the way certain traits or genetic conditions are passed down through the X chromosome, one of the 2 sex chromosome (X and Y) |
| sex-influenced inheritance | refers to traits that are controlled by genes on the autosomes (non–sex chromosomes) but are expressed differently in males and females because of the influence of sex hormones (like estrogen and testosterone) |
| sex-limited inheritance | refers to traits that are carried by genes present in both sexes, but the trait is expressed in only one sex — usually because of hormonal or anatomical differences. |
| What are the 2 sets of ducts that form near the unspecialized gonads in the indifferent stage of prenatal development? | -wolffian ducts -mullerian ducts |
| The probability that the daughter of a woman with a dominant disease-causing allele on one X-chromosome and a normal male will be affected with the disorder is ______ | 1/2 |
| In humans, if the SRY gene is not expressed, the unspecialized gonads develop into ________ | ovaries |
| The Royal families of England, Germany, Spain, and Russia suffered from the genetic disease hemophilia. T/F | True |
| Amad has scaly skin due to the x-linked recessive condition ichthyosis. He is ____________ for the trait. | hemizygous |
| With respect to the expression of x-linked genes, females are | genetic mosaics |
| Genomic imprinting is permanent in the somatic cells of a given individual. T/F | True |
| A female carrier of an x-linked trait who expresses the phenotype is called a __________ | manifesting heterozygote |
| The empiric risk that the monozygotic twin of a person with cleft lip also has cleft lip is _________ times the risk to a member of the general population who has no relatives with cleft lip. | 400 |
| Similarities between adopted people and the adoptive parents reflect mostly genetic influences. T/F | False |
| Geneticists designate heritability as "narrow" or "broad" to account for the fact that | genes contribute to different degrees. Typically, dominant alleles are rare and can have a large impact and recessive alleles tend to be common with minor but additive effects |
| Function of Leptin transporter | helps move leptin across the blood–brain barrier (BBB) so it can reach the hypothalamus. Once leptin is inside the brain, it: • Signals that the body has enough fat or energy stored • Reduces appetite • Increases energy use |
| Function of Melanocortin-4 receptor | is a protein found in the brain, mainly in the hypothalamus, that plays a crucial role in controlling: • Appetite (hunger and fullness) • Energy expenditure (how much energy your body burns) |
| Function of Leptin receptor | is a protein found on the surface of certain cells, especially in the hypothalamus region of the brain. Its main job is to receive signals from the hormone leptin, which is made by fat (adipose) cells. |
| Function of Leptin | -regulating appetite -controlling energy expenditure -reproductive function -modulates immune function -influences bone metabolism |
| A cohort study looks at | a large group of people over time, keeping track of specific health conditions or measures |
| Does the following statement describe a phenotype being influences by genes, the environment, or both genes and the environment: Exercise decreases the risk of heart disease. -genes -environment -both genes and environment | both genes and environment- ind genetic makeup can predispose to a high or lower risk of heart disease, choice to exercise is an env. factor that can impact that risk. Interaction btw a person's genetic and their lifestyle choices determines the outcome |
| Heritability refers to ______ | the genetic contribution to the variability of a phenotype in a population at a particular time |
| When a trait is polygenic, individuals cannot be categorized into classes with respect to their phenotypes. T/F | False |
| All the genes that influence a polygenic trait contribute equally ti the phenotype. T/F | False |
| The proportion of genes that two people with a certian relationship share is the | coefficient of relatedness |
| List the characteristics that distinguish single-gene diseases from other types of diseases. | Typically follow Mendelian inheritance patterns -autosomal dominant -autosomal recessive -X-linked Other diseases, such as miltifactorial disorders, are caused by a combination of genetic and environmental factors |
| Describe how Mendel deduced that recessive traits seem to disappear in hybrids. | experiments w/pea plants showed when he crossed 2 true breeding parents w/dif traits, the 1st generation all displayed dominant trait. The recessive trait seem to disappear. he deduced the recessive trait was not lost but was simply masked by the dominant |
| Define and distinguish heterozygote and homozygote; dominant and recessive; phenotype and genotype. | -homozygote has 2 identical alleles -heterozygote has two dif alleles -dom allele is 1 that its trait when only 1 copy is present -rec allele is 1 that its trait when 2 copies are present -geno is the genetic makeup -pheno is the observable |
| Explain how the law of segregation reflects the events of meiosis. | states that during the formation of gametes, the two alleles for a gene separate from each other so that each gamete carries only one allele |
| Indicated how a Punnett square is used to track inheritance patterns. | alleles of 1 parent along the top of the square, and alleles of the other parent are placed along the side. Each box rep a possible combo of alleles that offspring could inherit, allowing for calculation of probability of different geno and phenobarbitals |
| Explain how a gene alone may not solely determine a trait. | its expression can be influenced by other factors like -epistasis -polygenic inheritance -environmental factors -incomplete dominance and codominance |
| Autosomal recessive inheritance | The disease-causing allele is recessive and located on an autosome (non-sex chromosome). An individual must inherit two copies of the mutated allele (one from each parent) to be affected. Carriers, who have one copy of the allele, are typically unaffected |
| Explain how Mendel's experiments followed the inheritance of more than one gene. | dihybrid crosses involved tracking two different traits simultaneously, such as seed shape (round or wrinkled) and seed color (yellow or green). He crossed true-breeding parents allowing him to formulate the Law of Independent Assortment |
| Explain how the law of Independent assortment reflects the events of meiosis. | states that alleles for different traits are passed to offspring independently of one another. This reflects the events of meiosis, specifically metaphase I |
| Explain how pedigrees are used to show transmission of single genes. | shows the genetic relationships among family members and the inheritance of a specific trait over several generations. Squares represent males and circles represent females |
| Explain how exome and genome sequencing can reveal whether a sick child with healthy parents inherited 2 autosomal recessive mutations or has a new, dominant mutation. | can reveal whether a sick child with healthy parents inherited two autosomal recessive mutations or has a new mutation by comparing the child's DNA sequence to the parents' DNA sequences |
| Explain the effect of lethal alleles on Mendelian ratios. | alter Mendelian ratios because the homozygous recessive genotype (or sometimes the homozygous dominant genotype) results in the death of the organism, which is not represented in the surviving offspring |
| State how DNA structure underlies multiple gene variants | underlies multiple gene variants. A gene variant, or allele, is a different version of a gene. These variants arise from changes in the DNA sequence, such as single nucleotide polymorphisms (SNPs), insertions, deletions, or other mutations |
| Complete dominance | One allele completely masks the effect of the other allele in the heterozygous state. The phenotype of the heterozygote is the same as the phenotype of the homozygous dominant individual |
| Distinguish epistasis from interactions of alleles of the same genes | Epistasis: interaction btw 2 or more dif genes where 1 gene's effect masks or modifies the expression of another gene. Interactions of alleles of same genes: interact occur btw dif alleles of a 1 gene |
| Describe how penetrance, expressivity, and pleiotropy affect gene expression. | -Penetrance: proportion of ind w/ particular geno who actually express the associated pheno -Expressivity:degree to which a particular geno is expressed in individual's pheno -Pleiotropy: a single gene influences multiple, unrelated phenotypic traits |
| Explain how a phenocopy can appear to be inherited. | is an environmental caused trait that mimics a genetically determined trait. It appear to be inherited if environ factor is present across generations, leading to a similar pheno in related individuals, even though the underlying genotype is not the cause |
| Describe the mode of inheritance of a mitochondrial trait. | Maternal inheritance. Mitochondrial traits are inherited solely from the mother because the mitochondria in the zygote are derived exclusively from the egg cell. |
| Explain how mitochondrial DNA differs from DNA in the nucleus. | Mitochondrial DNA (mtDNA) is circular and in the mitochondria, while nuclear DNA is linear and located in nucleus. mtDNA is smaller, lacks introns, and is inherited maternally, while nuclear DNA is larger, contains introns, and is inherited both parents. |
| Explain how inheritance of linked traits differs from inheritance of genes on different chromosomes. | Linked traits are inherited together because their genes are located close to each other on the same chromosome, while genes on different chromosomes assort independently during meiosis. |
| Discuss the basis of linkage in meiosis. | is the tendency of genes located on the same chromosome to be inherited together. The physical proximity of genes on a chromosome prevents them from assorting independently during meiosis, unless a recombination event (crossing over) occurs between them. |
| Explain how linkage is used to derive genetic maps. | Genetic maps are derived by measuring the frequency of recombo between linked genes. The higher the recombination frequency, the farther apart the genes are on the chromosome. This allows scientists to determine the relative order and distance of genes. |
| Describe the factors that contribute to whether we are and feel male or female. | combo of genetic, hormonal, and environmental factors. Genetic factors, such as the presence of X and Y, determine biological sex. Hormonal influences play a crucial role. Gender identity, or how a person feels, is a complex psych and social construct |
| Distinguish between the X and Y chromosomes. | X chromosome is larger and contains many more genes than the Y chromosome. The Y chromosome contains the SRY gene, which is responsible for male sex determination. Females typically have two X chromosomes, while males have one X and one Y chromosome. |
| Discuss how manipulating the sex ratio can affect societies. | Can have significant social and economic consequences. An imbalance in the number of males and females can lead to social instability, increased competition for partners, and changes in marriage and family structures. |
| Distinguish between Y linkage and X linkage. | Y linkage refers to genes located on the Y chromosome, which are passed directly from father to son. X linkage refers to genes located on the X chromosome, which can be passed from mother to son or daughter, and from father to daughter. |
| Compare and contrast X-linked recessive inheritance and X-linked dominant inheritance. | X-linked recessive traits are more common in males bc they only have 1 X chromosome, so 1 recessive allele will be expressed. X-linked dom traits are expressed in both males and females, but an affected father will pass the trait to all of his daughters. |
| DIscuss the inheritance pattern of a trait that appears in only one sex. | A trait that appears in only one sex is often referred to as a sex-limited trait. The genes for these traits may be on autosomes or sex chromosomes, but their expression is limited to one sex due to hormonal or anatomical differences |
| Define sex-influenced trait. | is an autosomal trait that is expressed differently in males and females. The expression of the trait is influenced by the sex of the individual, often due to hormonal differences. |
| Explain why X inactivation is necessary. | to prevent female mammals from having twice as many X chromosome gene products as males, who only have one X chromosome. This process, also known as lyonization, ensures that the dosage of X-linked genes is equalized between males and females. |
| Explain how X inactivation is an epigenetic change. | bc it involves mod to the DNA/associated histones affect gene exp w/out changing the DNA sequence. DNA methylation and histone deacetylation, lead to form of Barr body, a trans inactive X chrom, which is a heritable change passed through cell divisions. |
| Discuss how X inactivation affects the phenotype in female mammals. | leads to a mosaic phenotype in female mammals. Because the inactivation of either the paternal or maternal X chromosome is a random process that occurs early in development, different cells in the female body will have different active X chromosomes. |
| Explain the chemical basis of silencing the genetic contribution from one parent. | leads to a mosaic phenotype in female mammals. Because the inactivation of either the paternal or maternal X chromosome is a random process that occurs early in development, different cells in the female body will have different active X chromosomes. |
| Explain how differences in the timetables of sperm and oocyte formation can lead to parent-of-origin effects. | through genomic imprinting.Genomic imprinting is an epigenetic phenomenon where certain genes are expressed in a parent-of-origin-specific manner. |
| Distinguish between single genes and polygenic traits. | Single genes are traits determined by the alleles at a single locus, while polygenic traits are determined by the combined effect of multiple genes |
| Define complex traits. | are traits that are influenced by multiple genes as well as environmental factors. These traits do not follow simple Mendelian inheritance patterns and often show a continuous range of phenotypes in a population |
| Explain how continuously varying traits reflect genetic and environmental influences. | such as height or skin color, reflect both genetic and environmental influences because they are determined by the cumulative effect of multiple genes (polygenic inheritance) and are also susceptible to environmental factors |
| Explain how determining empiric risk differs from calculating a Menelian frequency. | empiric risk is based on observation, while Mendelian frequency is based on theoretical probability. Mendelian frequency uses the known inheritance patterns of a single gene to predict the probability of a trait appearing in offspring |
| Define heritability. | is a measure of the proportion of phenotypic variation in a population that is due to genetic variation. It is a statistical estimate that indicates how much of the differences in a trait among individuals can be attributed to genetic factors |
| Discuss how studies on adpoted individuals and twins can indicate the extent to which a trait is inherited. | Studies on adopted individuals and twins are used to separate genetic and environmental influences on a trait |
| Explain the type of information that a genome-wide association study can reveal. | reveal associations between specific genetic variants, typically single-nucleotide polymorphisms (SNPs), and a particular trait or disease |
| Discuss how the methods discussed in the chapter can be applied to investigate variation in body weight. | can be applied to investigate variation in body weight by using a combination of approaches to understand the genetic and environmental factors |
| Autosomal dominant inheritance | The disease-causing allele is dominant and located on an autosome. An individual needs to inherit only one copy of the mutated allele from one parent to be affected. |
| Incomplete dominance | Neither allele is completely dominant over the other. The heterozygous phenotype is an intermediate blend of the two homozygous phenotypes. |
| Codominance | Both alleles are expressed equally and distinctly in the heterozygous state. Both phenotypes are visible simultaneously, not as a blend. |
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