Biology Cycle Test Term 3


Why are dogs different:

Millions of years ago people cross bread different dogs with different characteristics to make a litter of puppies with inherited aswell as new features and characteristics

Pug, Dalmation and Irish Wolfhound

How are their species Canis familiaris similar:

  • 4 legs
  • 1 tail
  • 2 eyes
  • 2 ears
  • fur 
  • tounge 

Genetic varitations: Earlobes not/attatched, tounge can/cannot be rolled, dimples yes/no, handedness right/left, middle finger hair/no hair

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 Chromosome- A thread-like structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.

23 chromosomes are given from the mother and 23  from the father.

The pairs in which chromosomes are known in are called homologous pairs (same structure). Humans have 23 pairs:

  • 22 pairs are autosomes (any chromosome except sex) 
  • 1 pair of sex chromosomes

Haploid number: Number of chromosomes in an egg or sperm cell (humans 23)

Diploid: Full number of chromosomes in all the other cells

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The Structure of a Chromosome

Gene: DNA that contains readable information

Before cell devision duplication of information takes place, thus forming 2 chromatids that are connected with a centromere

Related image ( 

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The Human Karyotype

Karyotype- Full set of 23 pairs of homologous chromosomes arranged in pairs and photographed through a microscope 

Mutation- When DNA is copied for cell division in some cases the order of chemicals are incorrect or part of a chromosome is missing 

A mutation is normally harmful towards the organisim and may therefore cause genetic diseases or death (colour-blindness and cystic fibrosis)

DNA fingerprinting can be used to compare a section of DNA from a person's body. A gel will help the sections form a pattern. Every persons is unique (not identical twins). The pattern can be useful in finding a matching suspect or how people are related


Homozygous: Having two of the same  alleles (dominant or ressesive)

Heterozygous: The two alleles will be different from one another. 

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