Flashcards in Chapter 3- Genes Deck (23):
How many DNA molecules in a cell?
46 in q human cell- but there are thousands of genes
Where are genes located?
A gene occupies a specific position on one type of chromosomes where this located this position is called the locus of a gene
Who is Gregor Mendel and what did he do?
He crossed varieties of pea plants and deduced that the differences between the varieties that he crossed together were due to heritable factors
What are alleles?
Various specific forms of gene
Alleles are alternative forms of the same gene there for what what do they have the same of?
The same locus- occupy the same position on one type of chromosomes
How do alleles differ from each other?
Differ from each other by one or a few bases
What's a single nucleotide polymorphism (SNPs)?
Position in a gene where more than one base may be present
How are new alleles formed?
By gene mutation
What type of mutation can occur to change an allele?
A base substitution - one base is replaced by a different base
What can some mutations do?
Mutations that develop into gametes can be passed on to offspring and cause genetic disease
What is a genome?
The genome is the whole of the genetic information of an organism
In humans what is it that the genome consists of?
46 molecules that form the chromosomes in the nucleus plus the DNA molecules in the mitochondrion
What is the human genome project?
The entire base sequence of human genes
What is a gene?
Is a heritable factor that consists of a length of DNA and influences a specific characteristic
Definition of a gene mutation
It is a change in the nucleotide sequence of a section of DNA coding for particular feature
What is the cause of sickle-cell anaemia?
Base substitution mutation
What does base substitution result in?
A change in a single messenger RNA codon during transcription
In sickle-cell anaemia what is the code on the exchange to result in a disease?
The 6th codon for the beta chain of haemoglobin is changes from GAG to GTG
The change of GAG to GTG does what?
Causes a change in mRNA codon (GAG to GTG) resulting in a single amino acid change of glu to val
What does DNA change due? What does messenger rna change to? What does it amino acid change to?
DNA = GAG to GTG
mRNA = GAG to GUG
Amino acid = glu to val
What does the amino acid alter?
Alters shape of haemoglobin - forms fibrous insoluble strands- red blood cells adopt a sickle cell shape
What are three bad consequences of sickle-cell Amenia?
1) insertable haemoglobin can't effectively carry oxygen which means they can be weakness, shortness of breath, tiredness
2) sickle-cell may accumulate in the capillaries and form clots, blocking blood supply to vital organs and causing health problems
3) cause anaemia (low RBC) as cells are destroyed more rapidly than normal RBC