Ch. 5 - Genetics

Question 1

DNA is composed of

Answer 1

Nucleotides

Question 2

Nucleotides are composed of

Answer 2

Phosphate group + deoxyribose sugar (backbone) + 1 of 4 nitrogenous bases
- Several hundred to ~1 million base pairs encodes information in the form of genes

Question 3

Nucleotide or nitrogenous bases

Answer 3

• Adenine and guanine (purines)
• Thymine, cytosine (pyrimidines)
• Uracil (RNA only)

Question 4

The human genome is distributed over 23 pairs of different

Answer 4

Chromosomes
- 22 pairs of autosomes
- 1 pair of sex chromosomes (XX or XY)

Question 5

DNA is tightly coiled into __________ and spooled around __________

Answer 5

Chromatin, histone proteins

Question 6

Each DNA/histone complex is called a

Answer 6

Nucleosome

Question 7

__________ are sequences of DNA that contains the instructions for making an RNA molecule

Answer 7

Genes

Question 8

A set of three bases on mRNA that codes for a specific amino acid

Answer 8

Codon

Question 9

Genetic cyclical pattern

Answer 9

A gene encodes a message, to build a protein, to enable some kind of form or function, that regulates a gene

Question 10

The process by which the genetic information in DNA is copied into a complementary strand of mRNA

Answer 10

Transcription
- Occurs in the nucleus (DNA never leaves the nucleus)
- DNA -> mRNA

Question 11

Steps of transcription

Answer 11

1. An enzyme called RNA polymerase binds to a specific DNA sequence (the gene)
2. It unzips the DNA and builds a strand of mRNA by matching RNA nucleotides (A, U, C, G) to the DNA template strand
3. The completed mRNA then leaves the nucleus and travels to a ribosome in the cytoplasm where protein synthesis/translation occurs
   - Result: a strand of mRNA carrying the genetic code for one protein

Question 12

The process where the mRNA sequence is decoded by ribosomes to build a specific protein

Answer 12

Translation
- Occurs in the cytoplasm at a ribosome
- mRNA -> protein

Question 13

Steps of translation

Answer 13

1. The ribosome reads the mRNA in groups of three bases (codons)
2. Each codon corresponds to a specific amino acid
3. Transfer RNA (tRNA) brings the correct amino acid to the ribosome, matching its anticodon to the mRNA codon
   4.The ribosome links the amino acids together to form a polypeptide chain
   - Result: a protein with a specific sequence and structure, determined by the original DNA code

Question 14

Gene expression

Answer 14

Genes can be turned on or off, and this involves many different transcription factors

Question 15

Something that turns a gene on

Answer 15

Induction

Question 16

Something that turns a gene off

Answer 16

Repression

Question 17

The study of changes in organisms due to changes in gene expression, not changes or mutation to DNA

Answer 17

Epigenetics (“above genes”)

Question 18

Epigenetic factors

Answer 18

• Growth and development
• Drugs and chemicals
• Environmental factors
• Aging
• Diet and exercise

Question 19

An individual’s genetic material

Answer 19

Genotype

Question 20

An individual’s recognizable physical or biochemical traits or characteristics

Answer 20

Phenotype

Question 21

Genes are found at a specific __________ on a chromosome

Answer 21

Locus

Question 22

Variants or alternate forms of a gene (one from each parent), usually created by mutations

Answer 22

Alleles
- Alleles may carry recessive or dominant traits
- A gene can have multiple potential alleles

Question 23

If both copies of a gene are alike, you are

Answer 23

Homozygous

Question 24

If both copies of a gene differ, you are

Answer 24

Heterozygous
- If you are heterozygous for a recessive trait and do not express/show it, you are called a carrier

Question 25

The ability of a gene to express its function

Answer 25

Penetrance

Question 26

Single-gene traits are unusual, as most are

Answer 26

Polygenic

Question 27

Patterns of inheritance dictate

Answer 27

How traits, including genetic disorders, are passed from parents to offspring

Question 28

A single copy of a particular gene on one of the non-sex chromosomes (autosomes) is sufficient to cause the trait or disorder

Answer 28

Autosomal dominant

Question 29

Two copies of a particular gene (one from each parent) on one of the autosomes are needed for the trait or disorder to be expressed

Answer 29

Autosomal recessive

Question 30

One particular gene on the X chromosomes causes the trait or disorder (dominant), or two copies are needed (recessive)

Answer 30

X-linked: dominant or recessive

Question 31

A type of DNA that is inherited exclusively from the mother

Answer 31

Mitochondrial inheritance - mtDNA; less common

Question 32

Mendelian laws of inheritance

Answer 32

Inheritance of single-gene traits is highly predictable - E.g., freckles (MC1R), earwax consistency (ABCC11), many monogenic disease traits like sickle cell disease, Huntington's disease - Predicting inheritance for polygenic traits is much more complicated