2.1 DNA Flashcards
What is DNA?
- DNA is short for deoxyribonucleic acid
- it is a set of coded instructions that produce all our proteins, this in turn determines our physical characteristics
What is the Structure of DNA and who first described it?
It is a double-helix structure, and it was first described by James and Francis Crick in 1953
What is the Watson-Crick model?
- It describes how DNA is the same overall structure for all organisms
- It is made up of smaller molecules called nucleotides
What does a nucleotide consist of?
- A phosphate group
- A deoxyribose sugar
- One of 4 nitrogenous bases
What are the 4 bases?
Adenine, thymine. guanine and cytosine
How are nucleotides composed?
A nucleotide is connected to other nucleotides to form a strand
- the phosphate and sugar group are always alternating
- the base is always attached to the sugar
What makes DNA a double helix?
DNA is composed of two strands of nucleotides linked together in a ladder
What is the backbone?
The backbone is made of alternating deoxyribose sugars and phosphate groups
What are the steps?
The nitrogenous bases
How are the bases joined?
They are joined by hydrogen bonds
What is complementary base pairing?
When the ‘A’ of one strand can only pair with a ‘T’ (2 hydrogen bonds),
and the ‘c’ of one strand can only pair with a ‘g’ on the other (3 hydrogen bonds).
What are genes?
Genes are segments of DNA that code for a particular protein, that is responsible for a particular physical trait.
What are the two ways genes are unique?
- The sequence of the bases (the unique code)
- The number of bases (length of the sequence)
What are chromosomes?
Chromosomes are packages of DNA
They consist of a very large section of DNA that is wrapped around proteins called histones.
Being tightly wrapped around histones allows such a large molecule to fit inside a cell.
Where is DNA found?
In the nucleus of the cell
What is karyotyping?
Karyotyping is sorting a jumble of chromosomes into matching pair based on size and banding pattern, in order to study the chromosomes of an individual.
What are autosomes?
Chromosome pairs 1-22 are known as autosomes
Sex chromosomes
- Pair 23
- XX female chromosomes
- XY males chromosomes
Y is shorter than X
What are banding patterns?
Bands along a chromosome.
Each band represents a gene. A single chromosome can have 1000s of genes.
What are homologous chromosomes?
- Chromosomes with matching banding patterns
- They have the same gene in the same location
Chromosome number
humans have a total of 46 chromosomes in their body cells.
However, and egg and sperm cell only have 23, and combine to form a zygote.
