EKB-Lecture 1

•Chromosomes are arranged in homologous pairs in the nucleus of eukaryotic cells. What is meant by the term homologous pairs?

Pairs of chromosomes that contain the same alleles
Pairs of chromosomes that are of a similar length and that have a similar gene positioning
Pairs of chromosomes that are inherited from one parent
Pairs of chromosomes that code for the same characteristic in different organisms

•Which of the following cells contains an odd number of chromosomes?

The muscle cells of birds
The kidney cells of mammals
A plant ovum (egg cell)
The nerve cells of a reptile
A human skin cell

•The diagram provided shows a karyotype, which is used to view the chromosomes in an organism. How are chromosomes 1–22 ordered in a karyotype?

By the number of genes they contain and in matching pairs
By decreasing size and in random pairs
By decreasing size and in homologous pairs
By increasing size and in matching pairs

•A carrot has 9 chromosomes in a haploid cell. How many chromosomes will a diploid body cell from this organism contain?

2
18
20
81

•A human ovum contains 24 chromosomes. It is fertilized by a sperm cell with the normal number of chromosomes. Which of the following is true about the zygote that will develop?

The zygote will fail to develop into an embryo.
The zygote will contain one too many chromosomes.
The zygote will contain the normal number of chromosomes, but these chromosomes will not pair correctly.
The zygote will contain an additional pair of chromosomes.

•Which of the following best describes the term chromosome?

A threadlike structure of tightly coiled DNA that contains many genes
An alternative form of a gene
A tightly coiled section of DNA that codes for a particular protein
A protein that DNA wraps around to increase its stability

•In a human ovum, which of the following chromosomes is larger in size than chromosome number 8?

23
21
22
None of the above

•Which of the following represents the correct sequence of the formation of a human embryo?

Fertilization —> mitosis —> meiosis
Fertilization —> meiosis —> mitosis
mitosis —> Fertilization —> meiosis
meiosis —> Fertilization —> mitosis

•Which of the following statements correctly describes both the sperm and the ovum?

Unlike somatic cells which contain autosomes, the sperm and the ovum are sex cells which contain a single pair of either X or Y chromosomes.
The sperm and the ovum are gametes which contain the same number of autosomes found in somatic cells, but each of them contains half the number of sex chromosomes found in the somatic cells.
The sperm and the ovum are haploid cells containing 22 autosomes and one sex chromosome responsible for sex determination; both cells are involved in sexual reproduction.
The sperm and the ovum are haploid cells containing 23 pairs of chromosomes, which is half the number of chromosomes found in the somatic cells.

•Assume that chromosome segregation did not take place properly during the formation of a human ovum. The karyotype of the resulting ovum is 23,O. If this ovum was fertilized by a normal sperm, which of the following statements would be correct?

The number of chromosomes in the zygote would be 46.
The number of autosomes in the zygote would not equal the normal number of autosomes in humans.
The ratio between the number of chromosomes in the zygote and the gametes would be 2 : 1.
All the answers are correct

•Which of the following best defines a diploid cell?

A cell that contains one copy of each chromosome
A cell that divides to form four identical daughter cells
A cell that contains two copies of each chromosome
A cell that contains two copies of each pair of homologous chromosomes

•The majority of human chromosomes are known as autosomes. How many chromosomes in a human karyotype of a somatic (body) cell are sex chromosomes?

8
4
2
6

•In humans, which of the following is considered the 8th chromosome in terms of size?

Chromosome X
Chromosome 8
Chromosome y
Chromosome 7

•Which of the following words describes sex chromosomes in human males?

Symmetric
Non homologous
Inconsistent
Irregular

Sec1 – U3: Inheritance of traits

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