7A: Genes and Chromosomes

Question 1

What is a genome, and what does it do?

Answer 1

The complete set of DNA in an organism’s haploid cells. In humans, almost every cell in the body contains a complete copy of the genome. The genome contains all of the information needed for development, function and reproduction.

Question 2

What is a gene?

Answer 2

A section of DNA that codes for a protein

Question 3

What is an allele?

Answer 3

The variations of a gene

A particular form of a gene with a unique nucleotide sequence.

Question 4

General trend in genome size and gene number in different cells?

Answer 4

Prokaryotes/viruses: 1 allele because of asexual reproduction (and identical daughter cells)
Eukaryotes: 2 alleles
Gene number also same.

Question 5

Why is the number of chromosomes in an organism not a reflection of their genetic complexity?

Answer 5

Genetic complexity is the number and organization of genes within its genome, not the number of chromosomes
Plants have more chromosomes than more complex organisms (gorillas)

Question 6

What is a nucleotide made of?

Answer 6

Phosphate group
Deoxyribose sugar
Nitrogenous base (adenine + thymine, guanine + cytosine)

Question 7

Organization of chromosomes from biggest to smallest?

Answer 7

Cell -> Nucleus -> Chromosome -> Chromatin -> Nucleosomes -> Histone -> DNA -> Base pairs

Question 8

What is a histone?

Answer 8

A protein that DNA coils around

Question 9

What is a nucleosome?

Answer 9

DNA coils are further coiled into super coils called nucleosomes

Question 10

Two types of macromolecules in chromosomes?

Answer 10

Nucleic acid and proteins (histone)

Question 11

What is DNA?

Answer 11

Polymer inside a nucleus with the genetic information responsible for the development and function of an organism

Question 12

What is aneuploidy?

Answer 12

Occurs in organisms which has an extra or missing chromosome (caused by non-dysjunction)

Question 13

When an organism is missing 1 chromosome, is it called ___?

Answer 13

Monosomy

Question 14

When an organism has 1 extra chromosome, is it called ___?

Answer 14

Trisonomy

Question 15

When an organism has 2 extra chromosomes, is it called ___?

Answer 15

Tetrasomy

Question 16

When an organism has an extra set of chromosomes (3 in each set), is it called ___?

Answer 16

Polyploidy

Question 17

How are karyotypes made?

Answer 17

Chromosomes are condensed and stained, and matched together. This occurs in metaphase.

Question 18

What is down syndrome?

Answer 18

Trisomy 21 - 3 chromosomes in the set

Question 19

What is Klinefelter syndrome?

Answer 19

When a male has an extra X chromosome (XXY)

Question 20

What is Turners syndrome?

Answer 20

When one X chromosome in a female is missing/partly deleted (XO)

Question 21

Does each gene always have exactly two alleles?

Answer 21

No, for example, the ABO blood type system (there are three)

Question 22

Are all genes made of the same nucleic acid monomers?

Answer 22

Yes, DNA and RNA which are made of the same monomers (A,C,G,T)

Question 23

What information is coded into DNA?

Answer 23

The instructions for all the proteins the organism will ever synthesize

Question 24

What does 3’ and 5’ mean?

Answer 24

Refers to the number of carbon atoms in a deoxyribose sugar molecule that a phosphate group binds to.

Question 25

Describe the general trend for genome size and gene number for viruses, bacteria, and eukaryotic organisms

Answer 25

Virus (small genome size, few number of genes) -> prokaryote (medium genome size and number of genes) -> eukaryote (large genome size, large number of genes)

Question 26

What is chromatin?

Answer 26

A complex of DNA and protein

Question 27

What is a chromatid?

Answer 27

One half of a replicated chromosome

Question 28

Differences between sex chromosomes and autosomes?

Answer 28

Autosomal genes determine most phenotypic characteristics, whereas sex chromosomes determine the biological sex

Question 29

Where is the same form of a gene found?

Answer 29

Sister chromatids