science - biology

DNA

• all genetic code to create proteins to form an organism

• Located in the nucleus

• DNA is wrapped tightly around proteins called histones to form a chromosome

Base pairs

• adenine

• Thymine

• Guanine

• Cytosine

Nucleotide

• smallest unit of DNA/single unit of DNA

• Nucleotide → dna → chromosome → genome → nucleus → cell

Chromosomes

• total of 46 chromosomes in humans

• Arranged in pairs based on length

→ 23 pairs of chromosomes → you in inherit 23 individual from each parent

Types of chromosome - sex chromosomes

• x or y

• 1 pair/2 individual

• XX - female

• XY - male

Types of chromosomes - autosome

• the other 22 pairs

• Their names are numbers based on length

• Ordered largest to smallest → 1 is largest 22 is smallest

Genes

• chromosomes are made up of them

• Sections of DNA that code for a trait

Gametes

• 23 chromosomes

• Sperm and egg cells

• Haploid number (n)

• 22 autosomes

• 1 sex chromosome

Somatic cells

• skin cells

• Liver cells

• Brain cells

• Diploid number (2n)

→ autosomes - 44

→ sex chromosomes - 22

mRNA role

• carries information from dna template to the ribosomes

• Found in nucleus

tRNA role

Transfers amino acids to ribosomes to add them to protein chain

• found in cytoplasm

DNA vs rna

• double helix vs single helix

• Uracil vs thymine

• Ribose sugar vs deoxyribose

Mutations

• a change that occurs in DNA which impacts the DNA sequence and therefore the codon, which shifts

• 3 types of- addition, substitution, deletion

Genes vs alleles

• genes are a type of trait category

• Allleles are specific types of the same gene

Karyotype

• a lab produced photograph of a complete set of chromosomes from a single individual

• These are organised based on numerical order

• Humans have 22 pairs of autosomes and one pair of sex chromosomes

Genetic disorders

• can be identified if there is an additional chromosome or not enough chromosomes

Cell division - meiosis

• creates gametes

• Process of crossing over creates unique chromosomes

• Results in 4 genetically unique gamete daughter cells

Cell division - mitosis

• creates somatic cells

• Results in 2 genetically identical daughter cells

Genotypes vs phenotypes

• phenotype - physical manifestation of a trait

• Genotype - genetic code for a particular trai

Alleles - dominant vs recessive

• dominant - represent with capital letter

• Recessive - represented with lowercase

Co dominance inheritance

• neither allele is dominant or recessive → both traits expressed

Sex-linked inheritance

• can be dominant, recessive or co-dominant

• Specific to sex chromosome → most are X-linked

What is evolution

• the process by which living things change and adapt over generations

What is variation

• variation in evolution is differences in characteristics between individuals within the same species or between different species

What is natural selection

• the process where organisms best suited to their environment survive, reproduce and pass in their traits

Natural selection

1. Variation

2. Selection pressures

3. Survival of the fittest

4. Population