Genetics Flashcards
Define Genetics
Study of heredity and how characteristics are passed on from one generation to the next
What are chromosomes?
Thread-like structures, found in the nucleus of each cell that carry genetic information
What are chromosomes made up of?
DNA and proteins
When can chromosomes be seen?
Only during cell division
How many pairs of chromosomes do humans have?
46 overall and 23 chromosomes pairs of chromosomes
22 of these pairs are called autosomes, they look the same in both males and females
The 23rd pair are sex chromosomes, different in males and females. Females have two copies of the X chromosomes while males have one X and one Y.
What are karyotypes?
When human chromosomes are lined up by size in their pairs.
What are Genes?
Genes are a length of DNA that contain information about a specific trait
Where are Genes found?
Chromosomes
What are Genes made up of?
DNA
What are alleles?
Variations on a gene that code for different variation of the same trait.
eg. Recessive and Dominant
N or n
What is the scientific name for DNA?
Deoxyribose nucleic acid
What is DNA?
Molecule that contains instructions an organisms needs to develop, live and reproduce. They are found in every cell and are passed from generations.
What is DNA made up of?
3 types of molecules called nucleotides
What are the three nucleotides that make up DNA?
- Sugar (deoxyribose)
- Phosphate
- nitrogenous base
What do nucleotides do to each other?
They link together to form long chains = polymer
What are the four different types of nitrogenous bases that occur in a DNA molecule?
Adenine
Thiamine
Guanine
Cytosine
What is the structure of a DNA molecule?
The sugar and phosphate form the backbone and the base links the two chains of backbones together.
Which bases link to each other?
A to T
C to G
What shape does a DNA molecule make?
Double helix
Why does DNA replication occur?
So that each new cell has the same DNA as the parent cell
What are the three types of Genetic Dominance?
Complete, incomplete and co-dominance
What is complete dominance?
Where one trait is dominant over another
When most traits are controlled by 1 gene, each gene has 2 alleles but only 1 is completely dominant
Give an example of Complete dominance
A purple (P) pea flower is bred with a white (w) flower, the White is recessive to the purple so all the offspring will be purple as it is dominant.
What is incomplete dominance?
Both alleles are equally dominant and become ‘blended’
Give an example of incomplete dominance
Crossing a Red (R) & White (W) flowers to produce a pink (RW) flower
What is co-dominance?
When both traits coexist together and both alleles appear in the phenotype.
Give an example for Co-dominance
Breeding a Red (RR) cow with a White (WW) creates a Roan (RW) a mixture of both
🐃 + 🐮 = 🐄
What is a diploid organism?
🚶
An organism with two copies of each chromosome
One from the mother and the other from the father
What is an haploid organism?
🐜
An organism with only one copy of each chromosome
What is a triploid organism?
🌻
An organism that has three copies of each chromosome
How many alleles can a person have?
Two as chromosomes only hold one and every person has two chromosomes.
Alleles make up a…
Person’s genotype
Traits the alleles result in is called a…
Phenotype
What are different variations of a gene called?
Alleles
What are the two steps of biological process?
Meiosis
Fertilisation
Define meiosis
Type of cell division that make gametes (sperm and egg)
What are gametes?
Sperm and eggs, they carry one allele per gene, but as humans need two alleles for each gene, one half of gametes gets one allele and the other gets the other half of alleles
Give an example of meiosis
Susan has the alleles Bb which B codes for brown eyes and b codes for blue eyes.
During meiosis half of Susan’s eggs will receive alleles for brown eyes and the other half will receive the allele for blue eyes.
What is fertilisation?
When an egg fuses with a sperm to form a new cell called a zygote. The zygote then grows into a baby
What does fertilisation do?
Combines the mother’s and father’s DNA to make a offsprings genotype
What does a punnet square do?
Used to predict the genotype and phenotype of the offspring
What is a pedigree?
A diagram that shows how individuals are related to one another. It allows you to track how alleles are passed on from parents to offspring across generations.
What is a mutation?
A sudden permanent change to a gene
State three reasons for a mutation to occur
Radiation, chemicals, heat
What are autosomes?
The 22 pairs of chromosomes not including sex chromosomes
What is the difference between a genotype and phenotype?
Genotype is the type of gene
Eg. TT, Tt, tt
Phenotype is the characteristic you see
Eg. Tall or short
