# 3.7.1 Inheritance Flashcards

What is a genotype?

The genetic make up on an organism. It describes ALL the alleles that an organism has.

What is an allele?

A different version of the same gene

What is a gene?

Short section of DNA made up of nucleotide bases, which codes for a specific order of amino acids which makes a protein.

What is a phenotype?

Observable characteristics due to environment and genetic makeup

What is a homologous pair?

A pair of chromosomes - maternal and paternal. Also known as a bivalent

What is a recessive allele?

An allele whereby you need 2 copies of it (homozygous) to express that characteristic. Its not expressed if the dominant allele is present.

What is a dominant allele?

You only need ONE copy of this allele to express this characterisitic

Homozygous dominant means?

Two dominant alleles present (in the genotype)

Homozygous recessive means?

Two recessive alleles present (in the genotype)

Heterozygous means?

One recessive and one dominant allele present (in the genotype)

A codominant allele is?

Where both alleles contribute/expressed in the phenotype

What are multiple alleles?

Where you have more than two alleles for a particular gene

In a diploid organism (human) how many chromosome pairs are there?

23

In meiosis what happens to the diploid number?

It becomes haploid - halves

Characteristics are determined by your allele combinations, how many alleles for each characteristics end up in the gamete?

1

Pure breeding plants are said to be

Homozygous

If there are 30 boys and 15 girls what is the ratio?

2:1

Why are actual ratios not exactly the same as theoretical ratios in genetics?

Because fertilisation of gametes occurs by chance - each time a gamete is fertilised, it is an independent event of what has gone before it.

How can you try and get theoretical ratios to match observed/actual ratios?

Increase sample size so its more representative

If you were to perform a statistical test on Mendelian genetics and you where looking at observed and expected ratios - what test would you do and why?

Chi Squared - because you are comparing observed and expected values and determining if there is a statistical difference

Suppose you obtained a chi squared value of 5 and the critical value was 5.99 (2dof) - what can you conclude?

Because the chi squared value is SMALLER than the critical value - you accept the null hypothesis and there is greater than a 5% probability that the difference in the results are due to chance. There is no significant difference.

Suppose you obtained a chi squared value of 8 and the critical value was 5.99 (2dof) - what can you conclude?

Because the chi squared value is LARGER than the critical value - you reject the null hypothesis and there is less than a 5% probability that the difference in the results are due to chance. There is a significant difference.

What is the difference between monohybrid inheritance and dihybrid inheritance?

Monohybrid is the inheritance of a SINGLE gene, dihybrid is the inheritance of TWO genes (that are located on different chromosomes)

Give an examples of a characteristic that involves multiple alleles

Blood groups - IA, IB and IO

Identify the chromosomes that determine sex

Sex Chromosomes - X and Y