Lecture 2-Genetics

Question 1

Chromosome

Answer 1

Highly ordered structure composed of DNA and proteins that carries genetic information

Question 2

Gene

Answer 2

A sequence of nucleotides that represents a functional unit of inheritance; a region of DNA that codes for a product, either RNA or protein

Question 3

Aspects of sickle cell mutations

Answer 3

Single mutation can give resistance to malaria

Double mutation gives the sickle cell disease

Question 4

Inherited gene complement

Answer 4

Mutations may be transmitted from one or both parents

Typically called the constitutional genome

Question 5

Acquired gene complement

Answer 5

A subset of cells in an individual that arose by clonal propagation from a single mutation in one cell (ex: cancer)

Question 6

Syndrome

Answer 6

Set of characteristics which occur together and are assumed to have a common basis
Not all characteristics occur in all affected individuals
Range of variability within a population

Question 7

Biochemical genetics

Answer 7

Subspecialty of genetics that deals with the diagnosis, treatment, and research of inborn errors of metabolism

Question 8

Inborn errors of metabolism

Answer 8

Genetically determined biochemical disorder in which a specific enzyme defect produces a metabolic block (can cause an accumulation of substrate or a deficiency of products)

Single enzyme defect
Recessive

Question 9

First four inborn errors of metabolism

Answer 9

Alcaptonuria, cysonuria, pentosuria, albinism

Question 10

Simple biochemical pathway

Answer 10

Precursor–A–B–product (with enzymes in between)

Question 11

Effects of blocks in the tyrosine to melanin pathway

Answer 11

If all functions correctly–tyrosine gets converted to melanin and a black/dark brown cat is produced

If pathway is blocked at last step–conversion is incomplete and a brown/grey cat is produced

If pathway is blocked at first enzyme (tyrosine oxidase) then an albino cat is produced

Question 12

Salvage pathways

Answer 12

Can be seen in more complex pathways. If there’s a mutation and a substrate cannot bee converted to the normal product, secondary pathways may show an increase in activity.

Avoid the over accumulation of a potentially toxic substance in cells.

Question 13

General clinical features of inborn errors of metabolism

Answer 13

Poor growth, mental retardation, problems with metabolism, neurological problems

Question 14

Hyperphenylalaninemias

Answer 14

Group of biochemical disorders related to the function of phenylalanine hydroxylase which converts phenylalanine to tyrosine

Question 15

Phenylketonuria

Answer 15

PKU
Mutation of phenylalanine hydroxylase prevents conversion of phenylalanine to tyrosine
PHE accumulates in cells–toxic
First genetic disease linked to mental retardation
Put patients on a low PHE diet

Question 16

Non-PKU hyperphenylalaninemias

Answer 16

About a ten fold increase in PHE levels

Less damaging

Question 17

Variant PKU

Answer 17

Between full PKU and non-PKU

Special diet but not as restrictive as full PKU

Question 18

Tetrahydrobiopterin

Answer 18

BH4
BH4 is a cofactor that can also cause PKU
This type of mutation requires supplements of neurotransmitters since BH4 is involved in the production of neurotransmitters

Question 19

Basics of human chromosomes

Answer 19

46 chromosomes in a somatic cell (23 pairs)
Members of a pair are homologous chromosomes (homologs)
One homolog from each parent (normally)

Question 20

Mitosis

Answer 20

Somatic division
2N–4C–2N
Interphase–DNA replicates, 2N becomes 4C
Prophase
Metaphase–most important phase for cytogenetics
Anaphase–centromeres divide
Telophase

Question 21

Meiosis

Answer 21

Germ cell division (reduction division)
2N–N
-at metaphase 1 homologous chromosomes pair
-in anaphase 1 centromeres remain together and homologs separate (REDUCTION DIVISION)
-Then the two chromatids separate in the second round of division

Question 22

Isodisomy

Answer 22

2 chromosomes from the same source (duplication of 1 chromosome)

Question 23

Heterodisomy

Answer 23

2 chromosomes from different sources

Question 24

Nullosomic

Answer 24

Missing a chromosome

Question 25

Spermatogenesis steps

Answer 25

• Original germ cell replicates via mitosis to generate a large population of spermatogonia which are 2N
• At some point one of these cells will enter meiosis
• DNA replicates to give a primary spermatocyte
• Cell divides and following reduction division becomes a secondary spermatocyte
• Second meiotic division results in haploid spermatids which will mature into sperm

1-spermatocyte–4 spermatids

Question 26

Oogenesis steps

Answer 26

• Oogonia (2N) replicate via mitosis, one will enter meiosis and become a primary oocyte
• First meiotic division results in two unequal daughter cells (receive equal DNA but one gets more cytoplasm–secondary oocyte)
• Secondary oocyte goes through the second meiotic division, cell receiving more cytoplasm is the egg.

Meiosis is not complete until fertilization, penetration stimulates the last round of division