3.1 Genes Flashcards
What is DNA also known for?
Being the genetic blueprint
What does DNA code for and determine?
The characteristics of an organism
What type of features does DNA code for?
Physical
Behavioural
Physiological
What is DNA packaged and organised into?
Discrete structures called chromosomes
What is a gene?
The sequence of DNA that encodes for a specific trait
Is a specific trait influenced always by only one gene?
No sometimes it is influenced by multiple genes
What is the locus?
The position of a gene on a particular locus
What is the plural of locus?
Loci
What are alleles?
Alternative forms of a gene that code for the different variations of a specific trait
As alleles are alternative forms of the one gene, what do they possess?
Very similar gene sequences
By how much do alleles differ from one another?
By one or a few bases
What is an example of a characteristic that the gene has alleles that encode for different colours?
Hair or eye colour
What is a gene mutation?
A change in the nucleotide sequence of a section of DNA coding for a specific trait
How are new alleles formed?
By mutation
What are the three types of gene mutations?
Beneficial
Detrimental
Neutral
What do beneficial mutations do?
Change the gene sequence to create new variations of a trait
What do detrimental mutations do?
Shorten the gene sequence to stop the normal function of a trait
What do neutral mutations do?
Have no effect on the functioning of a specific function
What are beneficial mutations also known as?
Missense mutations
What are detrimental mutations also known as?
Nonsense mutations
What are neutral mutations also known as?
Silent mutations
What is an example of a disorder caused by a gene mutation?
Sickle cell anaemia
How did the sickle cell anaemia allele arise?
From a base substitution mutation
What is a base substitution mutation?
Where a single base is changed in the gene sequence
Where is the change that causes sickle cell anaemia?
The 6th codon for the beta chain of haemoglobin
How does the DNA sequence change in sickle cell anaemia and on what strand?
The DNA sequence changes from GAG to GTG on the non transcribed strand
How does the mRNA sequence change in sickle cell anaemia and in what position?
From GAG to GUG at the 6th codon position
What does the polypeptide change from in sickle cell anaemia?
From glutamic acid to valine
What does the change from Glu to Val do in sickle cell anaemia?
Alters the structure of haemoglobin causing it to form insoluble fibrous strands
What causes an individual suffering from sickle cell to feel constantly tired?
The insoluble haemoglobin cannot carry oxygen as effectively
What causes the shape of a red blood cell to a sickle shape in sickle cell anaemia?
The formation of fibrous haemoglobin strands
What causes the low red blood cell count in sickle cell anaemia?
Sickle cells are destroyed more rapidly than normal cells
What can cause myriad health issues in sickle cell anaemia?
Sickle cells may form clots within the capillaries which blocks blood supply to vital organs
What is a genome?
The totality of genetic information of a cell, organism or organelle
What does the genome include?
All genes as well as non-coding DNA sequences
What does the human genome consist of?
46 chromosomes
3 billion base pairs
21,000 genes
What was the human genome project?
An international venture to sequence the human genome
What did the human genome project show?
That humans share the majority of their sequence
What did the human genome project showed contributed to diversity?
Short nucleotide polymorphisms
What were the four outcomes the completion of the human genome project lead to?
Mapping
Screening
Medicine
Ancestry
How did the human genome project help with mapping?
The number, location, size and sequence of human genes is now known
How did the human genome project help with screening?
It has helped the production of specific gene probes to detect sufferers and carriers of genetic diseases
How did the human genome project help with medicine?
The discovery of new proteins has led to improved treatments
How has the human genome project helped with ancestry?
Comparisons with other genomes has shown insight into the origins, evolution and migration patterns of man
Why is the number of genes present in an organism not a valid indicator of biological complexity?
As the number of genes will differ between species
What is the number of genes in a genome usually predicted by?
Identifying sequences common to genes
What may identifying regions may include?
Expressed sequence tags or sequences that are homologous to known genes
What makes accurate counts of unique gene numbers very difficult?
The presence of pseudogenes and transposons
WHy may final estimations of gene numbers vary significantly?
As scientists may use different approaches to predict gene numbers
