Lecture 1 Flashcards
describe Human Variation
Variation may be discrete or continuous, but both are genetic in origin
give an example of and explain single gene human variation
Eye Colour is primarily determined by a single gene that has two possible alleles, brown (dominant) and blue (recessive).
Why can brown parents have blue children, but not vice versa?
chromosomes are in pairs, one from each ____.
____ are also in pairs.
genes controlling the same characteristics occupy identical positions on _______ chromosomes.
the gene pairs control one _______.
the genes of a corresponding pair are called _____.
alleles are _______ ____ of the same gene.
homologous chromosomes have the same ____ and carry the same gene ______.
chromosomes are in pairs, one from each parent/
genes are also in pairs.
genes controlling the same characteristics occupy identical positions on homologous chromosomes.
the gene pairs control one characteristic.
the genes of a corresponding pair are called alleles.
alleles are alternative forms of the same gene..
homologous chromosomes have the same length and carry the same gene sequences
describe inheritance of eye colour
brown is the dominant allele, blue is recessive
dominant allele expresses colour, so if baby is homozygous brown, or heterozygous it must have brown eyes, homozygous blue means it will have blue eyes
describe The Male-Determining Gene
Males have a Y chromosome which has the male determining gene “Sex Reversed on the Y (SRY)”
SRY switches on genes to force the gonads to develop in a male-like fashion and produce testosterone.
Testosterone travels around the blood stream, enters cells via Androgen receptors (AR) and switches on male genes.
how can a female have an X and Y
Androgen Insensitivity Syndrome Also known as Testicular Feminisation Syndrome X-linked recessive trait Gene encodes androgen receptor Mutant gene makes no functional receptor SRY gene makes functional SRY protein Gonads develop as testis Testis produce androgens Androgens have no effect
ow are genes passed on from parent to child?
Genes in the cell nucleus are physically located on 23 pairs of chromosomes
One set of 23 chromosomes is inherited from each parent
Therefore, of each pair of genes, one is inherited from a person’s mother, and one from their father
how are genetic disorders classified
Alterations in single genes
Variants in genes
Chromosomal imbalance
describe Single gene disorders
Some medical conditions are caused by a change in just one or both copies of a particular pair of genes. These are called “single gene disorders”.
The three common types of single gene disorders are called:
•Autosomal dominant
•Autosomal recessive
•X-linked
Dominant- These individuals are called Heterozygotes with one copy of the altered gene they are affected
Recessive-Homozygotes must have two copies of the altered gene to be affected
X-linked recessive- Males with an altered gene on the X- chromosome are always affected
give Examples of Autosomal Dominant Conditions
- Huntington disease
- Neurofibromatosis type 1
- Marfan syndrome
- Familial hypercholesterolemia
- Familial Adenomatous Polyposis (FAP)
- Prader-willi
describe marfan syndrome
a genetic disorder of the connective tissue • Heart, lungs and CNS problems • Very Tall • Eye Lens dislocation • Arachnodactyly (long fingers and toes)
give Examples of Autosomal recessive conditions
- Sickle Cell disease
- Cystic fibrosis
- Batten Disease
- Congenital deafness
- Phenylketonuria (PKU)
- Spinal muscular atrophy
- Recessive blindness
- Maple syrup urine disease
describe cystic fibrosis
The cystic fibrosis transmembrane conductance regulator (CFTR) gene controls the movement of salt and water in and out of your cells, so the lungs and digestive system become clogged with mucus, making it hard to breathe and digest food
describe sickle cell anaemia
- Caused by a defective allele for the synthesis of haemoglobin (HBB).
- Abnormal HBB is produced which can lead to sickle shaped red blood cells and blockage of capillaries.
- Bony infarctions in the phalanges and metacarpals leads to uneven finger length.
describe parents Autosomal recessive inheritance
Parent who are carriers for the same autosomal recessive condition have one copy of the usual form of the gene and one copy of an altered gene of the particular pair
A parent who is a carrier passes on either the usual gene or the altered gene into the eggs or sperm. The other parent who is also a carrier for the same condition passes on either the usual gene or the altered gene into
his/her eggs or sperm
