Biology Flashcards
What are the building blocks of DNA?
Nucleotides
What are the components of a nucleotide?
Phosphate group, Pentose sugar, Nitrogenous bases
What Components form the DNA backbone?
Sugar and phosphate
What components form the rungs?
The nitrogenous bases
What are the four types of nitrogenous bases?
Adenine, Thymine, Cytosine and Guanine
What is complementary base pairing?
bases bonding with one other specific base
Why does DNA have a double helix?
To make it more compact
Where is the DNA located in the cell?
The nucleus holds DNA (genetic information)
How is DNA organised in the nucleus?
It’s organised into units called genes, genes are found on chromosomes.
What is a gene?
A segment of DNA that codes for a particular protein (e.g eye colour)
How many pairs of chromosomes do humans have?
23 pairs or 46 total
What does diploid mean?
A paired set of chromosomes in somatic cells
What is a somatic cell?
Cells of the body except sex cells
What are gametes?
Reproduction or sex cells (sperm and egg)
What does haploid mean?
The possession of one copy of each chromosome in a cell.
What sex chromosomes do females have?
XX
What sex chromosomes do males have?
XY
What is an autosome?
Any chromosome not included in sex determination
What is a sex chromosome?
The chromosomes that determine an individuals sex
What is a karyotype?
A karyotype is the visualisation of an individual’s collection of chromosomes
What is the purpose of a karyotype?
To look at abnormal numbers or structures of chromosomes
What is a homologous chromosome?
The same size, shape and carry the same genes
Where do you get the matching pairs?
One of the pair from your Mother and one of the pair from your Father
What is an allele?
A different version/form of a gene, e.g brown eyes, blue eyes
What is the difference between a gene and an allele?
A gene specifies a trait, allele specifies the form a gene takes
What are dominant alleles?
Alleles that will always be expressed when they’re present
What are recessive alleles?
Alleles that are only expressed when there are two recessive alleles
What is a genotype?
The alleles that a person has e.g Bb
What is a phenotype?
The trait that is seen e.g brown eyes
What does homozygous mean?
the same alleles e.g BB or bb
What does heterozygous mean?
Different alleles e.g Bb
What is a genetic cross?
Genetic crosses are used to measure the probability for a specific cross
What’s a punnet square?
A tool to do a genetic cross
How to complete a genetic cross?
- Designate characters to represent alleles (e.g, A = dark red cross; a = light red
- Write the genotype and phenotype of the parents (e.g, dark red cross Aa x Aa)
- Use a grid to work out gamete combinations
- Write the genotype and phenotype ratios of offspring
What is a pedigree chart?
It is a chart of the genetic history of a family over several generations
What symbols are used?
Female: circle, Male: square
How do you determine if the pedigree chart shows an autosomal or x-linked disease/trait?
