Genetics and Mutations
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Questions and Answers

What is the primary effect of fertilization on genetic variation?

  • It decreases genetic variation by ensuring identical offspring.
  • It enhances genetic variation by randomly combining parental chromosomes. (correct)
  • It generates new alleles through chromosomal crossover.
  • It prevents the transmission of hereditary traits.

A test cross is performed on an individual displaying a dominant phenotype. The purpose of this cross is to:

  • Force the individual to become homozygous recessive.
  • Identify new mutations within the individual’s genome.
  • Determine if the individual is homozygous or heterozygous for the trait. (correct)
  • Determine the rate of chromosomal aberration.

If two genes show a 10% recombination frequency, approximately how far apart are they on the chromosome?

  • 100 centimorgans
  • 1 centimorgan
  • 0.1 centimorgans
  • 10 centimorgans (correct)

Which of the following best describes the function of a self-cross?

<p>To determine whether alleles are dominant, recessive, co-dominant, or lethal. (B)</p> Signup and view all the answers

Why might a mutation go unnoticed in an organism?

<p>The mutation is a silent mutation and does not affect the phenotype. (C)</p> Signup and view all the answers

What is the significance of independent assortment (interchromosomal recombination) in gamete formation?

<p>It randomly distributes chromosomes into gametes, increasing genetic diversity. (C)</p> Signup and view all the answers

How do environmental factors influence genetic variation?

<p>Environmental factors can cause mutations, which may introduce new alleles. (D)</p> Signup and view all the answers

In genetics, what does a dihybrid cross specifically help to determine?

<p>The inheritance pattern of one or two traits, including whether genes are linked. (C)</p> Signup and view all the answers

Which type of mutation results in a change in the amino acid sequence due to an alteration in the reading frame?

<p>Frameshift mutation (D)</p> Signup and view all the answers

A point mutation causes a codon to change from encoding a certain amino acid to a stop codon. What kind of mutation is this?

<p>Nonsense mutation (D)</p> Signup and view all the answers

A single nucleotide substitution occurs in a coding region, but the amino acid sequence of the protein remains unchanged. What is this type of mutation called?

<p>Silent mutation (C)</p> Signup and view all the answers

What term describes the presence of multiple alleles for a gene within a population?

<p>Genetic polymorphism (B)</p> Signup and view all the answers

If a particular allele is found at a frequency of 2% within a population, how would it be described?

<p>Polymorphic allele (C)</p> Signup and view all the answers

Restriction fragment length polymorphisms (RFLPs) are primarily caused by what?

<p>Variations in DNA sequence recognized by restriction enzymes (A)</p> Signup and view all the answers

Why are RFLPs useful in parenthood assessment?

<p>Each offspring inherits a unique combination of RFLPs from both parents. (C)</p> Signup and view all the answers

Considering the use of DNA in forensic science, what principle ensures that each individual (except identical twins) has a unique genetic profile?

<p>The high degree of genetic polymorphism across the genome. (C)</p> Signup and view all the answers

If a child's DNA fingerprinting shows bands not present in either parent, which of the following explanations is LEAST likely?

<p>The child inherited a rare allele from both parents that was not detectable in their DNA fingerprinting. (A)</p> Signup and view all the answers

A population of butterflies consists of two color morphs: orange and white. If the orange morph becomes significantly more common over several generations, which factor is MOST likely at play?

<p>Natural selection favoring the orange morph due to increased camouflage. (D)</p> Signup and view all the answers

A small group of individuals from a large, diverse population colonizes a remote island. What is the MOST likely consequence for the genetic diversity of the island population?

<p>The genetic diversity will decrease due to the founder effect. (C)</p> Signup and view all the answers

In a population of birds, a new allele arises that confers resistance to a common parasite. Which of the following is MOST likely to occur over time?

<p>The frequency of the resistance allele will increase due to natural selection. (A)</p> Signup and view all the answers

Two geographically separated populations of squirrels, initially very similar, begin to show noticeable differences in coat color and tail length over many generations. What is the LEAST likely explanation for these differences?

<p>Gene flow between the two populations is high, maintaining similarity. (D)</p> Signup and view all the answers

Which of the following scenarios would be LEAST conducive to maintaining genetic equilibrium in a population?

<p>Strong natural selection pressures. (A)</p> Signup and view all the answers

A population of fish in a lake is divided into two sub-populations by the introduction of a dam. Over time, these sub-populations begin to exhibit genetic differences. What is the primary mechanism driving this divergence?

<p>Reduced gene flow between the sub-populations. (B)</p> Signup and view all the answers

Within a population, a particular allele has a frequency of 1.0. What can be definitively concluded about this allele?

<p>The allele is fixed in the population. (A)</p> Signup and view all the answers

Why does the 'weeding out' of less adapted traits in a population NOT lead to the development of a 'perfect organism'?

<p>Non-favored alleles are retained in small proportions, allowing for potential re-increase under different circumstances reflecting adaptation to a specific set of conditions rather than perfection. (D)</p> Signup and view all the answers

What is the significance of finding common alleles across all human populations when studying human genetics?

<p>It indicates that 'race' is an arbitrary construct rather than a scientifically valid biological classification, as no population has a unique set of alleles. (C)</p> Signup and view all the answers

How has the progress in human genetics impacted family planning and reproductive health?

<p>It has made it possible for couples to evaluate the risks of abnormalities in their offspring and detect them in the embryonic stage. (B)</p> Signup and view all the answers

A recessive allele will only be expressed in which of the following individuals?

<p>Homozygous individuals, both male and female (D)</p> Signup and view all the answers

What kind of information can a pedigree analysis reveal about a specific gene?

<p>Whether the gene is autosomal or sex-linked and whether it is dominant or recessive. (B)</p> Signup and view all the answers

If both parents are heterozygous for a recessive genetic disorder, what is the probability that their child will be affected by the disease?

<p>25% (A)</p> Signup and view all the answers

Why does a pedigree analysis only give assumptions, and not certainties, about inheritance?

<p>Pedigrees are based on probabilities and observed phenotypes, which may not always reflect the underlying genotypes due to factors like incomplete penetrance or new mutations. (D)</p> Signup and view all the answers

How do genes located on the homologous segment of sex chromosomes (X and Y) typically behave?

<p>They act like autosomal genes. (D)</p> Signup and view all the answers

If a disease-causing allele carried on an autosome is dominant, what is the likelihood of a heterozygous parent passing on the allele to their child, assuming the other parent is normal?

<p>50% (A)</p> Signup and view all the answers

In the context of allele frequencies, what is the most accurate interpretation of 'survival of the fittest'?

<p>Organisms that are best suited to their current environment are more likely to survive and reproduce, increasing the frequency of their alleles. (B)</p> Signup and view all the answers

In males (XY), how are alleles located on the non-homologous part of the X chromosome expressed?

<p>They are always expressed, whether dominant or recessive. (C)</p> Signup and view all the answers

A couple undergoes genetic testing and discovers they both carry a recessive allele for a particular disease. Which statement accurately describes the potential inheritance pattern of this disease in their offspring, assuming autosomal inheritance?

<p>There is a 25% chance that each child will inherit the disease, a 50% chance they will be carriers, and a 25% chance they will not have the allele. (C)</p> Signup and view all the answers

Which prenatal diagnostic method involves analyzing the karyotype of the fetus to detect chromosomal abnormalities?

<p>Chromosomal analysis (D)</p> Signup and view all the answers

Which of the following prenatal diagnostic techniques can detect abnormalities in protein synthesis?

<p>Biochemical analysis (B)</p> Signup and view all the answers

A couple is undergoing prenatal testing. Which test would directly identify a specific mutation in the nucleotide sequence of a gene?

<p>DNA analysis (B)</p> Signup and view all the answers

Why is advanced maternal age (typically over 35 years) a factor in recommending prenatal testing for chromosomal abnormalities?

<p>The risk of chromosomal abnormalities in the fetus increases with maternal age. (D)</p> Signup and view all the answers

A male who is heterozygous for Huntington's disease marries a female who is also heterozygous for the trait. What percentage of their offspring are likely to be heterozygous for Huntington's disease?

<p>50% (A)</p> Signup and view all the answers

Which type of mutation is most likely to lead to premature chain termination during protein synthesis?

<p>Nonsense mutation (B)</p> Signup and view all the answers

In a dihybrid cross with linked genes, crossing-over occurs during meiosis. This process allows for the formation of what type of gametes?

<p>Parental and recombinant (D)</p> Signup and view all the answers

If one parent dies from lung cancer, their child is not necessarily at a greater risk than others whose parents did not develop cancer. How can cancer be caused by mutations and yet not be heritable?

<p>Mutations caused by environmental agents, like tobacco smoke, cannot be inherited. (B)</p> Signup and view all the answers

Which of the following crosses would always result in offspring that display the dominant phenotype?

<p>Both TT × tt and TT × TT (B)</p> Signup and view all the answers

According to the following pedigree, the original parents of this family had (Assume that photo1692528067 represents a pedigree showing two parents with 2 daughters and 1 son).

<p>2 daughters and 1 son (C)</p> Signup and view all the answers

Sexual reproduction favors which of the following outcomes at the population level?

<p>Genetic diversity (D)</p> Signup and view all the answers

Autosomal recessive diseases are transmitted from parents to offspring. An affected person cannot descend from which of the following parental combinations?

<p>One normal homozygous dominant and another heterozygous parent (D)</p> Signup and view all the answers

Flashcards

RFLP and DNA Fingerprinting

Method to analyze variations in DNA among individuals, linking offspring to parents' DNA.

Population

Members of a species living in the same area at the same time, interacting more with each other than others.

Gene Pool

Total set of alleles in a population, representing genetic diversity available for inheritance.

Phenotypic Variability

Differences in physical traits among individuals in a population due to different allele combinations.

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Genetic Equilibrium

State where allele frequencies in a population remain stable over time, indicating no evolution.

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Evolution

Change in allele frequency in a population over time, driven by mechanisms like natural selection and mutation.

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Migration and Gene Flow

Movement of individuals into or out of a population that alters allele frequencies and gene pool composition.

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Natural Selection

Process by which certain traits become more common in a population because they confer an advantage for survival and reproduction.

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Substitution mutation

A mutation resulting from replacing a nucleotide pair in DNA with a different pair.

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Missense mutation

A substitution mutation that causes a change in the amino acid sequence.

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Nonsense mutation

A substitution that creates a new stop codon, terminating protein synthesis.

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Silent mutation

A mutation that changes the nucleotide sequence without changing the amino acid sequence or protein function.

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Frame-shift mutation

Mutations caused by deletions or insertions that shift the reading frame of the DNA sequence.

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Locus

The precise location of a gene or allele on a chromosome.

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Genetic polymorphism

The presence of multiple alleles for a gene in a population, with an allele frequency greater than 1%.

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RFLP (Restriction Fragment Length Polymorphism)

Variations in DNA sequences used as genetic markers, resulting from differences in restriction maps.

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Independent Assortment

The process where gametes get unique combinations of chromosomes during meiosis.

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Genetic Variation

Differences in alleles among individuals enhance diversity in a population.

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Monohybrid Cross

A genetic cross examining one trait with two contrasting alleles.

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Dihybrid Cross

A cross that explores two traits simultaneously, either independent or linked.

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Test-Cross

A method to determine if an individual with a dominant phenotype is homozygous or heterozygous.

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Centimorgan

A unit measuring genetic linkage, indicating distance between genes based on recombination frequency.

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Environmental Mutations

Mutations caused by external factors that can affect DNA, leading to potential phenotypic changes.

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Recessive Allele Expression

A recessive allele is expressed only in homozygous individuals, both male and female.

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Heterozygous Parents Risk

When both parents are heterozygous, there is a 25% chance for a child to be affected by a recessive disease.

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Sex Chromosome Segments

X and Y chromosomes have homologous and non-homologous segments affecting gene expression differently in boys and girls.

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Girls and Sex-linked Alleles

Girls (XX) express sex-linked alleles like autosomal traits, having two copies on X chromosomes.

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Boys and X-linked Alleles

Boys (XY) express sex-linked alleles from the X chromosome regardless of dominance due to a single copy.

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Prenatal Diagnosis Methods

Procedures like amniocentesis and chorionic villus sampling determine if a fetus is affected by diseases.

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Chromosomal Abnormalities

Chromosomal analysis detects structural and numerical abnormalities but can't identify gene mutations.

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Gene Therapy Status

Gene therapy for some conditions is experimental and not widely available yet.

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Huntington's Disease Genetics

If both parents are heterozygous, 25% of offspring will be heterozygous.

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Linked Genes and Crossing-over

Dihybrid cross with linked genes results in parental and recombinant gametes.

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Cancer Mutation Heritability

Cancer mutations usually occur in somatic cells, not inherited.

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Dominant Phenotype Cross

Only a TT × tt or TT × TT will always yield dominant phenotype offspring.

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Sexual Reproduction Advantage

Sexual reproduction promotes genetic diversity in populations.

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Autosomal Recessive Conditions

Diseased offspring may not arise from two homozygous parents.

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Homologous Chromosomes

Chromosomes that have the same genes but may have different alleles.

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Allele Frequency

The proportion of different alleles in a population's gene pool.

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Survival of the Fittest

Theory that organisms better adapted to their environment tend to survive and produce more offspring.

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Phenotypic Differences

Observable characteristics in individuals, such as skin or hair color.

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Human Populations

Groups of humans defined by shared genetic or phenotypic traits.

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Biological Markers

Specific genetic traits used to identify differences between populations.

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Pedigree Analysis

A diagram showing the genetic relationships and phenotypes of a family over generations.

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Autosomal Dominant Inheritance

A pattern where only one copy of a dominant allele is needed for a trait to be expressed.

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Heterozygous Parent

An individual with two different alleles for a specific gene.

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Study Notes

Genetics

  • Offspring resemble parents but are not identical due to genetic recombination
  • Chromosome structure includes centromere, p arms, and q arms.
  • Diploid organisms have two copies of each chromosome (one from each parent)
  • Alleles are different versions of a gene
  • Homozygous: identical alleles
  • Heterozygous: differing alleles
  • Dominant allele is expressed in the phenotype
  • Recessive allele is masked in the phenotype
  • Co-dominant alleles both contribute to the phenotype
  • Incomplete dominance: dominant allele is not fully expressed
  • Meiosis randomly distributes alleles, increasing genetic diversity
  • Fertilization combines genetic material, further increasing diversity through random union of gametes
  • Recombination during prophase I of meiosis results in new combinations of alleles on homologous chromosomes

Genetic Recombination

  • Crossing-over (a type of recombination): homologous chromosomes exchange DNA fragments during prophase I.
  • Intrachromosomic recombination: recombination WITHIN a chromosome
  • Interchromosomic recombination: recombination between homologous chromosomes, independent assortment of chromosomes to daughter cells
  • Fertilization increases genetic variation by random combination of chromosomes from parents.
  • Genetic variation occurs during meiosis and fertilization
  • 1% recombination = 1 centimorgan genetic distance between genes on a chromosome

Mutations and Polymorphism

  • Mutations are changes in DNA sequence that can be caused by environmental factors or errors in DNA replication
  • Substitutions (missense, nonsense, silent): change in nucleotide pair
  • Deletions/Insertions (frameshift mutations): change the reading frame leading to different amino acid sequences
  • Mutations may be harmful, beneficial, or have no effect on phenotype
  • Silent mutations: don't affect the phenotype
  • Polymorphism: the presence of multiple alleles for a gene in a population. It is present at a frequency > 1% in a population.
  • Polymorphism in coding and non-coding regions of DNA.

Genetic Variation in Populations

  • Population: members of a species in a specific geographical area.
  • Population's gene pool: complete set of alleles in a population
  • Genetic variability: difference in alleles within a population
  • Allele frequencies can change due to migration (gene flow), natural selection, and mutation
  • Stable gene pool indicates population at genetic equilibrium; changes in allele frequency over time is termed as evolution.

Human Genetics

  • Human genetics studies hereditary diseases and traits
  • Pedigree analysis: tracing traits through generations, and helps diagnose if trait is autosomal recessive or dominant and helps determine if it is sex-linked
  • Genetic testing / diagnostic: helps detect abnormalities for early intervention of diseases
  • Prenatal diagnosis: allows for determination of fetal health / genetic issues
  • Chromosomal analysis (karyotyping): visual inspection of chromosomes, this shows structural or numerical abnormalities. This determines the chromosome structure and composition as well as the number of chromosomes
  • Biochemical analysis: to determine protein abnormalities.
  • DNA analysis: to detect abnormal nucleotide sequences.

Specific Questions (from last page of document)

  • Question 1: If a male is heterozygous for Huntington's disease, and marries a female heterozygous for the trait, 50% of their offspring will be heterozygous
  • Question 2: A mutation causing premature chain termination is called a nonsense mutation.
  • Question 3: In a dihybrid cross with linked genes, crossing-over creates parental and recombinant gametes
  • Question 4: A parent with lung cancer does not necessarily increase the risk of offspring inheriting the cancer. Most cancers are somatic mutations not germ-line mutations.
  • Question 5: The cross TT x tt will always display a dominant phenotype (all offspring will be heterozygous or have the dominant trait)
  • Question 6, 7, 8, 9, 10, 11, and 12: refer to the pages for the details of the specific questions. These questions concern specific genetic traits, patterns, and calculations rather than broad concepts which are already covered in this summary.

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Test your knowledge of genetics. Questions cover fertilization, test crosses, recombination frequency, self-crossing, mutations, independent assortment, environmental factors influencing genetic variation, dihybrid crosses, and types of mutations.

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