Genetics

Question 1

What is a genotype?

Answer 1

A genotype is a person’s genetic
composition. It is the actual genes specific to the individual. I

Question 2

What is a phenotype?

Answer 2

A phenotype is a person’s observable characteristics

Question 3

What is a Punnett Square?

Answer 3

A Punnett Square is a grid
used to show the gametes of each parent and their possible offspring. It is used to predict the
transmission of genetic diseases.

Question 4

What is a nucleoside and what does it consist of?

Answer 4

Nucleosides are precursors to the formation of nucleotides. They consist of a nitrogen base and a
five-carbon sugar (ribose or deoxyribose). They are transformed into a nucleotide with the
addition of a phosphate group.

Question 5

What is a nucleotide?

Answer 5

Nucleotides are precursors to the formation of DNA and RNA and participate in metabolic pathways such as protein synthesis, energy metabolism, signal
transduction and regulation of enzyme activity.

Question 6

What are the bases of nitrogen?

Answer 6

The nitrogen bases are either purine or pyrimidine-based. Purines include adenine and guanine and are used in the formation of DNA and RNA. Pyrimidines include cytosine, thymine, and uracil. They too are used in the formation of DNA and RNA.

Question 7

What does DNA consist of?

Answer 7

DNA is composed of nucleotides and exists in the form of a double helix. The four nucleotides that form DNA include adenine, thymine, guanine, and cytosine. Adenine pairs with thymine while guanine pairs with cytosine. DNA functions to provide a code for all protein synthesis.

Question 8

What is a gene?

Answer 8

A gene is a portion of the DNA that contains the code for the sequence of amino acids in a protein. A gene can contain a variable number of nucleotides

Question 8

What is a codon?

Answer 8

A codon is a sequence of three nucleotide bases that provide the code for amino acids and are part of the gene.

Question 9

When does DNA synthesis occur?

Answer 9

DNA synthesis occurs during the S phase of cell
reproduction in the cell nucleus. The DNA unwinds, breaks, builds a new nucleotide chain, and mends back together. This process requires the use of the enzyme DNA polymerase. DNA provides the code for all of the body’s proteins.

Question 10

What does DNA polymerase do?

Answer 10

DNA polymerase acts as a proofreader to ensure that the appropriate bases are paired. An alteration in the sequence of DNA is the basis of mutations.

Question 11

What is RNA?

Answer 11

RNA is formed from DNA in a process that is called
transcription and requires the enzyme RNA polymerase. RNA serves as the bridge between DNA and protein synthesis. RNA is the workhorse for the code contained in the DNA. It controls how the information on DNA is used.

Question 12

What are the bases in RNA?

Answer 12

RNA includes adenine, uracil, guanine, and cytosine.

Question 13

Where does transcription occur?

Answer 13

In the cell nucleus

Question 14

What are the three types of RNA?

Answer 14

Messenger RNA, Ribosomal RNA, and Transfer RNA

Question 15

What does messenger RNA do?

Answer 15

Messenger RNA carries the information on how to build a protein. It contains the codons

Question 16

What does ribosomal RNA do?

Answer 16

Ribosomal RNA is used to form ribosomes which are the part of the cell that assists with the assembly of proteins.

Question 17

What does transfer RNA do?

Answer 17

Transfer RNA binds to the messenger RNA and an
amino acid, thereby assisting with the formation of a protein

Question 18

What is the process known as translation?

Answer 18

Translation is the process of protein synthesis. Messenger RNA is transcribed from DNA. Then
via translation, tRNA matches mRNA codons with specific amino acids to form a protein.

Question 19

What can human cells be divided into?

Answer 19

Human cells can be divided into gametes (sperm and eggs) and somatic cells (all other cells).

Question 20

What are gametes?

Answer 20

Gametes are haploid in nature which means they contain only 23 chromosomes. They reproduce by a process called meiosis which results in a daughter cell with 23 chromosomes. When the sperm and egg join, the two sets of 23 chromosomes form a complete set of 46 chromosomes.

Question 21

What are somatic cells?

Answer 21

Somatic cells are diploid in nature which means they contain 46 chromosomes or 23 pairs of chromosomes. They reproduce by mitosis, which results in a daughter cell that has 23 pairs of chromosomes or 46 chromosomes total.

Question 22

What are autosomal chromosomes?

Answer 22

Autosomal chromosomes are all chromosomes that do not have any relation to gender. Twenty-two of the twenty-three pairs of chromosomes are said to be autologous, which means gender has no bearing. Both males and females have the same 22 pairs of chromosomes.

Question 23

What are sex chromosomes?

Answer 23

Sex Chromosomes are the 23rd pair of chromosomes which is solely responsible for determining
gender. Females have two homologous X chromosomes and males have a pair of
nonhomologous chromosomes, X and Y. Disorders which are related to this 23rd pair of chromosomes are called sex-linked disorders.

Question 24

What is polyploidy?

Answer 24

Polyploidy is the state of having one or more extra sets of chromosome pairs. This is incompatible with life and the fetuses are often miscarried.

Question 25

What is aneuploidy?

Answer 25

Aneuploidy is an alteration in the chromosomal number. It results in a single missing or one
extra chromosome. It is caused by a nondisjunction which is a failure of the chromosomes to divide properly. This gives rise to cells that have an uneven number of chromosomes, such as 45 or 47 instead of 46.

Question 26

What are the two main types of aneuploidy?

Answer 26

There are two main types of aneuploidy, monosomy and trisomy. Monosomy is the state of having one chromosome in a pair missing. Trisomy is the state of
having more than two chromosomes in a pair.

Question 27

What is an example of monosomy?

Answer 27

Turner syndrome is an example of a sex-linked monosomy. In Turner syndrome, the person only has 45 chromosomes. The 23rd pair of chromosomes is missing the X component. This disorder only affects females.

Question 28

What are examples of trisomy?

Answer 28

Down’s syndrome is an autosomal trisomy. In this
disorder, the individual has three chromosomes on the 21st pair of chromosomes, instead of the normal two. Klinefelter’s syndrome is a sex-linked trisomy. This is the state of having two or more X chromosomes with one Y chromosome. The genotype will look like xxx/y.

Question 29

What is deletion and what is an example of it?

Answer 29

A deletion is a condition in which chromosomes are broken and DNA is lost. Cri du chat syndrome or the “cry of the cat” is a disorder that occurs because of a chromosomal deletion. It is characterized by a distinct cry of the baby, developmental delays, low birth weight, mental retardation, heart defects, and missing kidneys.

Question 30

What is a dominant allele?

Answer 30

A dominant allele is an allele that masks the presence of another allele in the phenotype. Of the pair of alleles on a chromosome, the dominant is the one whose effects are observable in the phenotype.

Question 31

What is a recessive allele?

Answer 31

The recessive allele is an allele that is masked in the phenotype by the presence of another allele. Of the pair of alleles, the recessive one is the one whose effects are usually hidden, not expressed.

Question 32

What is a homozygous allele?

Answer 32

Two dominant or two recessive alleles are called homozygous alleles because the genotypes of the two alleles are identical for a particular trait. This is called a homozygous genotype.

Question 33

What is a heterozygous allele?

Answer 33

When a dominant and recessive allele are present, then they are said to be heterozygous allele

Question 34

What is Huntington’s disease?

Answer 34

Huntington’s disease is a neurological degenerative disorder that is characterized by dementia and uncontrolled movements of the limbs. Onset is about age 40-50, and it is caused by a diseased, dominant allele (gene).

Question 35

What is cystic fibrosis?

Answer 35

Cystic fibrosis is an autosomal, recessive disorder that is most common in Caucasians. One in twenty-five Caucasians are carriers. The mutation leads to
improper coding of the chloride ion channels in the plasma cell membranes of epithelial cells of the lungs and pancreas. The defective transport system leads to a sodium imbalance and causes cell dehydration resulting in thick secretions that clog up the respiratory system, the pancreas, and reproductive systems.

Question 36

What is phenylketonuria?

Answer 36

Phenylketonuria is caused by a recessive gene that
has a homozygous recessive genotype. This genetic dysfunction results in a deficiency of the enzyme phenylalanine hydroxylase. This enzyme is responsible for the metabolism of the essential
amino acid phenylalanine. Without this enzyme, the phenylalanine will build up and result in brain damage and mental retardation if not caught early. Babies are tested at age three days for this, and if a diagnosis is confirmed, they are started on a special formula (and later maintained on a diet) that is low in phenylalanine.

Question 37

What are the most common sex-linked disorders?

Answer 37

The most common sex-linked disorders are X-linked recessive disorders. X-linked diseases are caused by a recessive allele that is always located on only the X chromosome. So the disorder is usually expressed in men only. Because women have two X chromosomes, the healthy X chromosome will compensate for the
mutated one