Inheritance and DNA Flashcards
(20 cards)
What does the nucleus contain?
The nucleus is where the genetic material, stored as linear chromosomes, is found in plant and animal cells
What is a chromosome?
A long thread-like structure made of DNA which is wrapped around proteins
What is a gene?
A short section of a chromosome/ region of DNA that codes for a particular functional RNA or protein; determines an organisms characteristics
What is an allele
Alleles are different versions of the SAME GENE- coding for slightly different RNA/protein (found at the same place on a chromosome/ locus)
What is meant by the term dominant?
A dominant allele is one that is expressed in the phenotype of an organism, even if ONLY 1 COPY is present
[represented by a capital letter]
What is meant by the term recessive?
A recessive allele is one that is NOT expressed in the phenotype unless 2 COPIES are present
[represented by a lower case letter]
What is meant by the term “homozygous”?
Homozygous is the word used to describe a genotype, where an individual has 2 alleles of a gene that are the SAME
What is meant by the term “heterozygous”?
Heterozygous is the word used to describe a genotype, where an individual has 2 DIFFERENT alleles of a gene
What is a genotype?
The genetic make-up of an organism
What is a phenotype
The appearance o an organism, resulting from the expression of its genes and its interaction with the environment
What type of allele causes the following genetic disorders: Cystic Fibrosis, Polydactyly and Huntington’s disease
Cystic fibrosis: RECESSIVE
Polydactyly: DOMINANT
Huntington’s disease: DOMINANT
What is meant by the term ‘genome’
The genome is the entire genetic material (DNA) of an organism
-complete set of genes
Where is DNA stored in a cell?
DNA is stored in long, thread-like structures called chromosomes, that are found in the nucleus of the cell
Describe the structure of DNA
- 2 very large polymers (polynucleotides)
- Each polymer is made of smaller sub units called nucleotides joined together by chemical bonds
- 2 strands bonded by hydrogen bonds b/t bases
- bases pair (A-T),(C-G)
- Strands twist in a helical shape; form double helix
What are nucleotides?
Monomers that make up each strand of DNA
- Made up of 3 main components: sugar (deoxyribose), a phosphate and a nitrogenous base
- The only thing that changes in different nucleotides are the bases
- There are 4 different nucleotides; 4 different bases: A, T, C, G
- Nucleotides joined by a bond b/t sugar and phosphate (sugar-phosphate backbone)
What is a gene? what does a gene control/ affect?
- A section of the chromosome
- Each gene stores the information needed to make a protein as a genetic code
- Genes code for proteins
Describe how the cell uses the genetic code to produce proteins
- Each section of a gene is made up of 2 DNA strands
- Th cell uses the base sequence on one strand (template strand) to make a protein
- The cell reads the genetic code as triplets
- Each triplet is made up of three bases
- And codes for one amino acid in the protein
- Certain triplets code for the same amino acid
- The cell uses the DNA to ensure amino acids are joined in the correct order
What is a gene mutation?
- A gene mutation is a change in an organism’s DNA
- It causes a change in the order of bases in the DNA
- This change in the base sequence may change a triplet in a gene
- The triplet may code for a different amino acid
- This may cause a change in the structure of the protein produced.
How can a mutation have an affect on an organisms phenotype?
“disturbing enzymes used to catalyse reactions that determine an organisms phenotype”
- Enzymes are proteins that must have a specific structure in order to function efficiently
- The shape of the active site must be complementary to the substrate in order for the enzyme to be able to catalyse a reaction
- A mutation may change a DNA triplet in a gene which codes for an enzyme
- Causes the triplet to code for a different amino acid
- Results in an enzyme with an active site which is no longer complementary to the substrate
- Produces a non-functional enzyme
- Affects the phenotype of an organism
How much of an effect do mutations have on an organisms phenotype?
USUALLY, little to NO EFFECT:
-There are large sections of DNA between the genes on a chromosome which do not code for proteins
-Mutations that occur in DNA that does not code for proteins are unlikely to affect the phenotype of an organism
-Silent mutations can occur:
The mutation changes the order of bases in the DNA, but this change does not affect the order of amino acids in the protein
OR
The mutation changes one of the bases in the triplet but the triplet still codes for the same amino acid
(described as silent as it has no effect on the phenotype of the organism)
