HL IB Biology - Inheritance
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Questions and Answers

What is the definition of phenotype?

  • The observable characteristics of an organism (correct)
  • The structural elements of DNA
  • The combination of alleles for a gene
  • The genetic makeup of an organism

Which of the following factors can influence an organism's phenotype?

  • Combination of genotype and environment (correct)
  • Environmental factors only
  • Genotype only
  • Mutation of a single allele

What is true about dominant alleles?

  • They can be masked by recessive alleles
  • They always lead to a dominant phenotype
  • They require both parents to express the phenotype
  • They need to be inherited from one parent to be expressed (correct)

How do recessive alleles affect phenotype expression?

<p>They are expressed only when inherited from both parents (B)</p> Signup and view all the answers

Which statement correctly describes the relationship between alleles and genotype?

<p>Genotype is the combination of alleles for a specific gene (B)</p> Signup and view all the answers

What is the expected ratio of phenotypes in a dihybrid cross of Drosophila for the given genes?

<p>9 : 3 : 3 : 1 (A)</p> Signup and view all the answers

What can the chi-squared test help determine in the Drosophila experiment?

<p>If variations are likely due to chance (A)</p> Signup and view all the answers

What fraction represents the expected number of flies with the black body and curved wings phenotype?

<p>3/16 (D)</p> Signup and view all the answers

In the context of the chi-squared test, what does a high chi-squared value, such as 235, indicate?

<p>The differences between observed and expected data are likely not due to chance (A)</p> Signup and view all the answers

Which component must be determined to use the chi-squared test effectively?

<p>The degrees of freedom from the results (A)</p> Signup and view all the answers

What type of inheritance is illustrated by the ABO blood groups?

<p>Co-dominance (A)</p> Signup and view all the answers

Which genotype corresponds to blood group A?

<p>IAIA or IAi (A)</p> Signup and view all the answers

What can result from using the wrong blood group in a transfusion?

<p>Immune response leading to clotting (D)</p> Signup and view all the answers

Which of the following alleles is recessive in the ABO blood group system?

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

How many alleles control a person's blood group in the ABO system?

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

In a Punnett square, what is the purpose of predicting the outcome of blood group inheritance?

<p>To anticipate the likelihood of blood group variations (B)</p> Signup and view all the answers

What antigens does genotype IBi produce?

<p>Antigen B only (C)</p> Signup and view all the answers

If both parents are heterozygous for blood groups A and B, what is the probability of producing a type O offspring?

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

What combination of sex chromosomes do females have in humans?

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

Which chromosome pair is responsible for sex determination in humans?

<p>Pair 23 (C)</p> Signup and view all the answers

Who determines the sex of the child in humans?

<p>The father (D)</p> Signup and view all the answers

How are sex chromosomes inherited from the father?

<p>Half of the sperm carry an X chromosome and half a Y chromosome (D)</p> Signup and view all the answers

What are chromosomes 1-22 classified as in humans?

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

In a genetic diagram to show sex inheritance, what replaces the usual alleles?

<p>X and Y chromosomes (B)</p> Signup and view all the answers

What characteristic do mammals share regarding sex chromosomes?

<p>The rule of XX for females and XY for males (D)</p> Signup and view all the answers

What is the result of fertilization by an X chromosome-carrying sperm?

<p>The child will be female (A)</p> Signup and view all the answers

What is the likelihood of the offspring of PKU carrier parents having PKU?

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

How are genetic conditions such as PKU typically screened for in newborns in the UK?

<p>Using a small prick of blood from the sole of the foot (B)</p> Signup and view all the answers

Which of the following is true regarding the inheritance pattern of autosomal recessive conditions?

<p>Both parents must be affected for the child to be affected (D)</p> Signup and view all the answers

What do Single Nucleotide Polymorphisms (SNPs) represent in genetics?

<p>The bases that differ between two alleles (A)</p> Signup and view all the answers

What will happen if a diploid individual inherits more than two alleles for a gene?

<p>They will only inherit two of the possible alleles (B)</p> Signup and view all the answers

Why is it important to differentiate between upper and lowercase letters in genetic crosses?

<p>It reduces ambiguity during marking (A)</p> Signup and view all the answers

How can different alleles of a gene vary despite occupying the same locus?

<p>They differ by one or only a few bases (A)</p> Signup and view all the answers

What is a common outcome of even a small change in base sequence in a gene?

<p>A large knock-on effect on the phenotype (B)</p> Signup and view all the answers

What does the '7' in the gene CFTR signify?

<p>It is located on chromosome 7. (C)</p> Signup and view all the answers

Which of the following best describes the inheritance of the CFTR and coagulation factor X genes?

<p>They are found on different chromosomes and thus are not linked. (B)</p> Signup and view all the answers

What does the 'p' represent in the notation for chromosome structure?

<p>The short arm of the chromosome. (C)</p> Signup and view all the answers

Which characteristic increases the likelihood of gene linkage?

<p>Genes located on the same chromosome and arm. (D)</p> Signup and view all the answers

How does the numbering in gene location notation relate to proximity to the centromere?

<p>Lower numbers indicate closer proximity to the centromere. (D)</p> Signup and view all the answers

Which gene is associated with the disorder hemophilia?

<p>Coagulation factor X (C)</p> Signup and view all the answers

What is the significance of genes being located on the same arm of a chromosome?

<p>They are likely to be inherited together. (D)</p> Signup and view all the answers

What does the notation '13q34' indicate?

<p>The gene is on chromosome 13, long arm, positioned far from the centromere. (A)</p> Signup and view all the answers

Flashcards

Phenotype

The observable characteristics of an organism (seen by looking - like eye colour, or found - like blood type).

Genotype

The combination of two alleles for a gene that determines a characteristic.

Dominant Allele

An allele that only needs to be inherited from one parent for the characteristic to be expressed in the phenotype.

Recessive Allele

An allele that needs to be inherited from both parents for the characteristic to be expressed in the phenotype.

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Allele vs. Gene

An allele is a specific version of a gene. A gene is a segment of DNA that codes for a particular trait.

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Autosomal Recessive Inheritance

A pattern of inheritance where an individual needs two copies of a mutated gene (one from each parent) to express a trait.

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PKU (Phenylketonuria)

A genetic disorder where the body can't break down phenylalanine, an amino acid. This can lead to brain damage if untreated.

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Cystic Fibrosis

An inherited disorder that affects the lungs, pancreas, and other organs. It's caused by a mutation in the CFTR gene.

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Newborn Screening

Testing babies shortly after birth for specific genetic disorders.

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SNP (Single Nucleotide Polymorphism)

A variation in a single nucleotide at a specific position in the DNA sequence.

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Allele

An alternative form of a gene. A diploid individual inherits two alleles for each gene.

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Locus

The specific location of a gene on a chromosome.

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Human Genome Project

A global research effort to map and sequence the entire human genome.

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Multiple Alleles

A gene that has more than two possible alleles for a trait. For example, the ABO blood group system has three different alleles (IA, IB, and i).

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Co-dominance

Both alleles in a heterozygous genotype are expressed, resulting in both traits being present in the phenotype. In the ABO blood group system, IA and IB are co-dominant.

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ABO Blood Groups

A system for classifying blood based on the presence or absence of specific antigens (A and B) on the surface of red blood cells. There are four main blood groups: A, B, AB, and O.

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Antigens

Molecules on the surface of red blood cells that trigger an immune response. ABO blood groups are determined by the presence or absence of specific antigens.

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Blood Transfusion

The process of transferring blood from a donor to a recipient. Correct blood type matching is essential to avoid immune reactions that can be life-threatening.

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Sex Determination

The biological process by which the sex of an organism is established, often determined by specific chromosomes.

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Sex Chromosomes

A pair of chromosomes that determine an individual's sex. In humans, these are the 23rd pair: XX for females and XY for males.

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Autosomes

All chromosomes except for the sex chromosomes. They don't directly influence sex determination.

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Who decides the baby's sex?

The father determines the sex of the offspring because he contributes either an X or a Y chromosome, while mothers always contribute an X chromosome.

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Punnett Square

A diagram used to predict the possible genotypes and phenotypes of offspring from a cross between two parents, showcasing the inheritance of sex chromosomes.

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Meiosis in Sex Determination

During meiosis, the sperm cells produced by the father carry either an X or a Y chromosome, determining the sex of the offspring.

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XX vs. XY

XX combination results in a female offspring, while XY combination results in a male offspring.

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Sex Determination in Other Species

While XX and XY chromosomes apply to humans and most mammals, sex determination can vary in other species, including birds and some insects.

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Dihybrid Cross

A genetic cross involving two different traits, each controlled by a separate pair of alleles.

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Expected Ratio

The predicted ratio of different phenotypes in the offspring of a cross, based on Mendelian inheritance laws.

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Observed Ratio

The actual ratio of phenotypes observed in the offspring of a cross, which may differ from the expected ratio.

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Chi-Squared Test

A statistical test used to determine if the observed ratio of phenotypes in a cross differs significantly from the expected ratio, suggesting a deviation from Mendel's laws.

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Degrees of Freedom

The number of independent categories in a data set, minus one, which influences choosing the correct critical value in the chi-squared table for analysis.

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Gene Location

The specific position of a gene on a chromosome, often described with a unique identifier (e.g., 7q31.2).

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Chromosome Arm

The two arms of a chromosome, designated as 'p' for the short arm and 'q' for the long arm.

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Centromere

The constricted region of a chromosome that joins the two arms.

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Gene Linkage

The tendency for genes located close together on the same chromosome to be inherited together.

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Autosomal Linkage

Gene linkage that occurs on non-sex chromosomes (autosomes).

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CFTR Gene

The gene responsible for producing a protein that regulates chloride ion movement, mutations of this gene can lead to Cystic Fibrosis.

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Coagulation Factor X

A protein involved in blood clotting, mutations in the gene encoding this protein can lead to haemophilia.

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Compare Gene Locations

Using databases to compare the positions of genes on chromosomes between species, can reveal potential linkage or differences in inheritance.

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Study Notes

HL IB Biology - Inheritance

  • Genetic Inheritance & Genetic Crossing:

    • Gametes are sex cells (e.g., sperm and egg)
    • Eggs are larger than sperm, containing food for the embryo
    • Sperm have many mitochondria for energy
    • Fertilization: Fusion of gamete nuclei forming a zygote
    • Zygotes are diploid (two sets of chromosomes)
    • Gametes are haploid (one set of chromosomes)
    • Humans have 23 pairs of chromosomes, 22 autosomes and 1 sex chromosome
    • Meiosis produces sex cells with a single copy of each chromosome
    • Alleles are different forms of a gene

  • Inheritance: Terminology

    • Gene: Short length of DNA coding for a characteristic (and protein)
    • Allele: Variations of the same gene
    • Genotype: Combination of alleles an organism inherits
    • Homozygous: Two identical alleles at a locus
    • Heterozygous: Two different alleles at a locus
    • Phenotype: Observable characteristics
    • Dominant allele: Expressed even if only one copy is present
    • Recessive allele: Expressed only if two copies are present

  • Dominant & Recessive Alleles

    • Dominant alleles are expressed in the phenotype even if only one copy is present
    • Recessive alleles are only expressed if both copies (two) are present
    • Homozygous dominant: Two copies of the dominant allele
    • Homozygous recessive: Two copies of the recessive allele
    • Heterozygous: One copy of the dominant allele and one copy of the recessive allele

  • Incomplete & Codominance

    • Codominance: Both alleles are expressed equally in the phenotype
    • Example: Speckled chickens (both black and white feathers expressed)
    • Incomplete dominance: Both alleles are partially expressed in the phenotype
    • Example: Pink flowers (blend of red and white)

  • Inheriting Alleles

    • Phenotypic plasticity: The way a phenotype is expressed can vary during an organism's lifetime due to its environment.
    • Environmental factors can influence gene expression, impacting physical characteristics.
    • An example is the Himalayan rabbit—pigmentation occurs in cooler parts of the body.

  • Inheriting Recessive Alleles: Phenylketonuria (PKU)

    • PKU is a recessive genetic disorder
    • Caused by a mutation to the PAH gene, resulting in a non-functional enzyme
    • It leads to a buildup of phenylalanine in the body.

  • Multiple Alleles: ABO Blood Groups

    • Blood type is determined by multiple alleles (more than two possible alleles)
    • Example: Blood group A, B, AB, or O
    • Critical in blood transfusions

  • Sex Determination

    • Sex determined by chromosomes (e.g., XX for female, XY for male)
    • Males determine the sex of offspring
    • Females only have X chromosomes
    • One X chromosome from each parent determines the child's sex.

  • Sex Linked Disorders: Hemophilia

    • Sex-linked disorders are inherited on the X chromosome
    • Females (XX): Two X chromosomes
    • Males (XY): One X chromosome, one Y chromosome
    • Hemophilia: A sex-linked genetic disorder affecting blood clotting
    • Recessive allele on the X chromosome makes a person with hemophilia unable to clot blood properly
    • Males have a higher chance of having hemophilia due to only receiving one X chromosome

  • Pedigree Charts

    • Charts tracing inheritance of characteristics (often disease) across generations
    • Squares for males and circles for females
    • Shading or cross-hatching indicates affected individuals

  • Continuous Variation

    • Variation across a range (e.g., height, weight); influenced by many genes and environment
    • Characteristics can be quantitatively measured

  • Dihybrid Crosses & Unlinked Genes (HL)

    • Studying inheritance involving two characteristics; controlled by two different genes
    • Unlinked genes reside on separate chromosomes
    • Assortment: Alleles inherited independently of each other
    • Segregation: Homologous chromosomes separate during meiosis

  • Genes & Polypeptides: Skills (HL)

    • Using databases for gene location and protein structure
    • Comparing DNA, mRNA, and protein sequences between species
    • Locating and Identifying Genes' Positions on Chromosomes

  • Identifying Recombinants (HL)

    • Recombination frequency: Likelihood of crossing over between linked genes during meiosis
    • Test crosses help identify recombinants and identify linked genes

  • Statistical Analysis of Dihybrid Crosses (HL): Chi-squared Test

    • Analyzing if difference between expected and observed results is significant (due to chance or other factors)
    • Calculating chi-squared value
    • Comparing chi-squared value with critical values to determine probability
    • Probability is used to decide if the expected ratio differs from the observed ratio.

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HL IB Biology Inheritance PDF

Description

Test your knowledge on genetic inheritance and crossing in this HL IB Biology quiz. Explore essential concepts such as gametes, zygotes, alleles, and key terms in inheritance terminology. Perfect for students preparing for their assessments!

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