Which response describes the behaviour of chromosomes in metaphase I and anaphase II of meiosis?
In garden peas, the pairs of alleles coding for seed shape and seed colour are unlinked. The allele for smooth seeds (S) is dominant over the allele for wrinkled seeds (s). The allele for yellow seeds (Y) is dominant over the allele for green seeds (y). If a plant of genotype Ssyy is crossed with a plant of genotype ssYy, which offspring are recombinants?
A. SsYy and Ssyy
B. SsYy and ssYy
C. SsYy and ssyy
D. Ssyy and ssYy
What constitutes a linkage group?
A. Genes carried on the same chromosome
B. Genes whose loci are on different autosomes
C. Genes controlling a polygenic characteristic
D. Alleles for the inheritance of ABO blood groups
The allele for red flower colour (R) in a certain plant is co-dominant with the allele for white flowers (R’). Thus a plant with the genotype RR’ has pink flowers. Tall (D) is dominant to dwarf (d). What would be the expected phenotypic ratio from a cross of RR’dd plants with R’R’Dd plants?
B. 50% pink 50% white, and all tall
C. 1:1:1:1, in which 50% are tall, 50% dwarf, 50% pink and 50% white
5. Two genes A and B are linked together as shown below.
If the genes are far enough apart such that crossing over between the alleles occurs occasionally, which statement is true of the gametes?
A. All of the gametes will be Ab and aB.
B. There will be 25% Ab, 25% aB, 25% ab and 25% AB.
C. There will be approximately equal numbers of Ab and ab gametes.
D. The number of Ab gametes will be greater than the number of ab gametes.
A polygenic character is controlled by two genes each with two alleles. How many different possible genotypes are there for this character?
A cross is performed between two organisms with the genotypes AaBb and aabb. What genotypes in the offspring are the result of recombination?
A. Aabb, AaBb
B. AaBb, aabb
C. aabb, Aabb
D. Aabb, aaBb
The diagram below shows chromosomes during prophase I of meiosis. How many chromosomes and chiasmata are visible?
In peas the allele for round seed (R) is dominant over the allele for wrinkled seed (r). The allele for yellow seed (Y) is dominant over the allele for green seed (y).
If two pea plants with the genotypes YyRr and Yyrr are crossed together, what ratio of phenotypes is expected in the offspring?
A. 9 round yellow : 3 round green : 3 wrinkled yellow : 1 wrinkled green
B. 3 round yellow : 3 round green : 1 wrinkled yellow : 1 wrinkled green
C. 3 round yellow : 1 round green : 3 wrinkled yellow : 1 wrinkled green
D. 1 round yellow : 1 round green : 1 wrinkled yellow : 1 wrinkled green
What is a difference between autosomes and sex chromosomes?
A. Autosomes are not found in gametes but sex chromosomes are.
B. Sex chromosomes are found in animal cells and autosomes are found in plant cells.
C. Autosomes are diploid and sex chromosomes are haploid.
D. Sex chromosomes determine gender and autosomes do not.
The diagram below shows a cell in meiosis. What can be deduced from this diagram?
If red (RR) is crossed with white (rr) and produces a pink flower (Rr), and tall (D) is dominant to dwarf (d), what is the phenotypic ratio from a cross of Rr dd and rr Dd?
B. 50% pink, 50% white and all tall
If a person inherited an allele with the same base substitution mutation from both parents, what sequences could be altered from normal in the person’s cells?
A. One mRNA base sequence only
B. Two mRNA base sequences only
C. One mRNA base sequence and one polypeptide amino acid sequence only
D. Two mRNA base sequences and two polypeptide amino acid sequences only
What is the locus of a gene?
A. The proportion of the population that have the gene
B. The part of the phenotype that is affected by the gene
C. The position of a gene on a chromosome
D. The predicted effect of natural selection on the frequency of the gene
Which processes always occur in meiosis but not normally in mitosis?
I. Chiasmata formation
II. Recombination of genes
III. Separation of homologous chromosomes
A. I and II only
B. II and III only
C. I and III only
D. I, II and III
The diagram below shows the life cycle of a moss. The haploid chromosome number is shown as n and the diploid number as 2n. At which stage in the life cycle does meiosis take place?
Mendel crossed pure breeding (homozygous) tall pea plants that had coloured flowers with pure breeding dwarf pea plants that had white flowers. All of the resulting F1 plants were tall and had coloured flowers.
If Mendel had crossed these F1 plants with a pure breeding strain of dwarf pea plants with coloured flowers, what proportion of tall coloured plants would be expected in the offspring?
A gene has three alleles. How many different genotypes can be found for this gene?
A cross is carried out between two heterozygous individuals (AaBb) where the genes A and B are not linked genes. What would be the proportions of genotypic recombinants amongst the offspring of this cross?
What is the genetic cross called between an individual of unknown genotype and an individual who is homozygous recessive for a particular trait?
B. Hybrid cross
C. Dihybrid cross
D. F1 cross
What is the usual cause of Down’s syndrome?
A. 21 pairs of chromosomes
B. Trisomy 21
C. Non-disjunction of sex chromosomes
D. Fertilization of the egg by two sperm
Which enzyme is used to produce complementary DNA (cDNA) from mRNA?
A. Restriction endonuclease
B. Reverse transcriptase
C. DNA ligase
D. RNA primase
Which human trait shows a pattern of polygenic inheritance?
A. ABO blood type
B. Sickle cell anemia
C. Skin colour
D. Co-dominant alleles
If the haploid number of an organism is 8, how many different varieties of gametes are possible, not considering the effects of crossing over?
How does the X chromosome differ from the Y chromosome in humans?
A. The Y chromosome is longer.
B. Some genes on the X chromosome are absent from the Y chromosome.
C. The genes are the same but some on the Y chromosome are not expressed.
D. The X chromosome determines sex.
What are the functions of the polymerase chain reaction?
I. Copy fragments of DNA
II. Amplify fragments of DNA
III. Translate fragments of DNA
B. I and III only
C. II and III only
D. I, II and III
How does recombination normally occur for unlinked genes?
A. Crossing-over in Prophase I
B. Random chromosome assortment
C. Failure of spindles to form
D. Random gene mutations
Why is it sometimes difficult to identify how certain characteristics are inherited in humans.
A. Most genes are linked.
B. Rates of mutation are high.
C. The inheritance may be polygenic.
D. The environment varies so little.
What procedure is used to determine whether a chromosome is in excess or missing in an organism?
D. DNA fingerprinting
What feature demonstrates codominance in the inheritance of ABO blood groups?
A. When A antigens and B antigens are present on red blood cells.
B. When A antibodies and B antibodies are present in blood serum.
C. When IA and i alleles are expressed in homozygotes.
D. When IA and i alleles are expressed in heterozygotes.
Which event occurs first in meiosis?
A. Centromere appearance
B. Chiasmata formation
C. Crossing over
Alleles S and T are both dominant. In the theoretical cross ttSs × Ttss, which of the following offspring would show recombination?
A. TS, tS
B. TS, Ts
C. tS, Ts
D. TS, ts
Colour blindness in humans is caused by an X chromosome linked recessive allele. In the pedigree chart below which two individuals must, for certain, be carriers of colour blindness?
A. II and IV
B. I and III
C. II and III
D. I and II
The diagram below shows a cell undergoing meiosis. What is this stage of meiosis?
A. Anaphase I
B. Prophase I
C. Anaphase II
D. Telophase II
A pure breeding tall plant with smooth seeds was crossed with a pure breeding short plant with wrinkled seeds. All the F1 plants were tall with smooth seeds. Two of these F1 plants were crossed and four different phenotypes were obtained in the 320 plants produced.
How many tall plants with wrinkled seeds would you expect to find?
What are the possible outcomes of recombination?
I. A different combination of unlinked genes not seen in the parents
II. A different combination of linked genes not seen in the parents
III. The same combination of genes seen in the parents
A gene in cattle controls whether horns develop or not. When cattle without horns are mated together, none of the offspring ever has horns. A male with horns is mated with females without horns. If half of the offspring have horns and half do not, what is the conclusion?
A. The male is homozygous dominant.
B. The male is homozygous recessive.
C. The male is heterozygous.
D. Only males have horns.
Humans are in blood group M, N or MN. The alleles for blood group M (M) and blood group N (N) are co-dominant. Humans are also in blood group A, B, AB or O. The alleles controlling these blood groups are IA, IB and i.
If two parents have the genotypes ii MM and IA i MN what is the ratio of possible phenotypes of their offspring?