Inheritance (HL IB Biology)

Identical twins have the same DNA (genotype) but often display many observable physical differences (phenotype). Studies on twins have shown that one twin can be more susceptible to diseases like cancer or diabetes.

Which of the following statements best explains these differences between identical twins?

Which of the following statements about genes is not correct?

Which of the following statements about alleles are correct?

1. New alleles can arise through mutation.
2. There are two different versions, or alleles, of every gene.
3. Every eukaryotic cell contains two alleles of every gene.

Which of the following explains why the father determines the sex of offspring and not the mother?

Which of the following is not correct regarding online gene databases?

In humans, there are three alleles that determine blood groups, namely I^O, I^A and I^B. The frequency of the I^O allele in a particular population was found to be 0.72. There was an equal abundance of the remaining two alleles.

What would the frequency of the I^B allele be in this population?

If two genes are said to be linked, what is meant by the term 'linked'?

Fruit flies (Drosophila melanogaster) exhibit characteristics governed by the following pairs of alleles.

M = brown body, m = black body

R = red eyes, r = white eyes

These pairs of alleles can be assumed to be unlinked.

If two double-heterozygous flies are crossed and produce 160 offspring, what is the likely number of offspring with red eyes and a black body?

Events in meiosis play an important role in determining the inheritance of alleles. Which row of the table states the correct words to name the processes being described?

Two linked genes are denoted by the dominant alleles G and H. Their recessive counterparts are g and h respectively.

Which way of writing the allele combinations on their chromosomes best displays the linkage between the two genes?

The inheritance pattern of two separate genes was investigated in a double-heterozygous cross in watercress plants. A chi-squared test of phenotypic ratios of the two separate genes results in a χ² value of 3.5.

At a 5% probability level, the critical value of chi-squared is 7.8 for an experiment of this nature.

Which row of the table best describes a conclusion that can be drawn from this data?

Which row(s) below give(s) correct statements about continuous variation?

Over time, many dihybrid cross experiments of autosomally-linked genes in sweet pea plants (Lathyrus odoratus) have been carried out by reputed scientists.

Which of the following best explains the presence of some non-parental phenotypes in the offspring of such crosses?

Long hair in a species of rabbit is caused by the presence of the allele H^L. These rabbits have either very long hair or moderately long hair. The 'wild-type' short-haired rabbit possesses the allele H^S. The diagram below shows the results of two crosses involving one female and two male rabbits.

Which row of the table below shows the phenotypes of the rabbits with the genotypes H^LH^L and H^LH^S?

A species of plant can have either blue or white flowers. The colour of the flower is controlled by a single gene where the dominant allele codes for blue flowers. 

Two heterozygous plants are crossed; which of the observed outcomes matches up most accurately to the expected ratio of blue to white flowers. 

Two parents have an equal chance of having a child with blood groups A, B, AB, or O.

What are the genotypes of the parents?

A woman is a carrier of haemophilia; her husband does not have haemophilia. 

What are the possible genotypes of their children?

The pedigree diagram shows the inheritance of cystic fibrosis across 3 generations.

Identify the genotype of the individuals labelled 1, 2 and 3 in the pedigree diagram.

A couple are trying to decide whether their children may be at risk of inheriting Huntington's disease. One parent is heterozygous for Huntingtons and the other is a healthy individual. 

Calculate the % chance that their offspring are likely to suffer from the disease.

The pedigree diagram below shows the inheritance of haemophilia across three generations.

Identify the genotype of person Y.

Which of the following statements are true for the determination of sex?

1. The chromosomes inherited through the maternal gametes determine the sex of the offspring
2. Females have a larger quantity of DNA than males
3. Sex is determined by the 23rd pair of chromosomes in humans
4. Sex of an individual can be identified using an image taken of chromosomes during interphase

In rabbits, brown coat is dominant to black coat and long ears are dominant to short ears. Two rabbits are heterozygous for both characteristics.

What is the probability that their first offspring will have black coats and short ears?

Which of the following processes results in the production of recombinants?

I. Crossing over of bivalents
II. Independent assortment during meiosis I
III. Independent assortment during meiosis II 
IV. Mutation

The inheritance pattern of two separate genes was investigated in a double-heterozygous cross in domestic cats (Felis catus). A chi-squared test of phenotypic ratios of the two separate genes results in a χ² value of 7.96.

The table below shows the critical values of the chi squared distribution. 

Which row of the table best describes a conclusion that can be drawn from this data?

In a breeding experiment, a tall, round seeded (homozygous dominant) pea plant was crossed with a short, wrinkled seeded (homozygous recessive) pea plant. The F₁ dihybrid plants were then used in a test cross.

If the genes are always linked and no crossing over occurs, what would be the predicted ratio in the F₂ generation?

In a variety of roses, P is the allele for pink petal colour and D is the allele for double flower.

Which cross will give a 1:1:1:1 ratio of phenotypes in the offspring?

The pedigree chart below shows the inheritance of Tay-Sachs disease which is an autosomal recessive trait, characterised by neurological problems caused by the death of nerve cells. 

In the pedigree chart, a filled in circle or square means the individual is affected and shows the genetic condition.

What is the probability that individuals 3 and 4 will have another child with Tay-Sachs disease?

Which statements best explain why the ABO blood system in humans is an example of co-dominance?

1. Allele I^A and the allele I^B are both expressed in the heterozygote/AB type blood.
2. Neither allele I^A or the allele I^B can mask the expression of the other allele.
3. There are three alleles of the gene that controls the blood group.
4. There are more than two blood groups.

Two parents with normal factor VIII have a child with haemophilia.

Which is the correct statement?