Human biology year 10

cells contain

cells contain smaller structures called organelles

Cells

are the basic building blocks of all living things

Organelles

have specific functions within a cell

Cell membrane

barrier around the cell and allows materials to pass in and out of the cell

Cytoplasm

jelly like substance inside the cell that provides structure and contains organelles

Nucleus

contains DNA and controls cellular functions

Nuclear membrane

membrane that encloses the nucleus

Genetics

is the study of how the characteristics and qualities of parents are given to their offspring through their genes.

The way in which traits are passed on from one generation to another was first explained by

Gregor Mendel

how did gregor mendel explain the way traits are passed down, In the 1850’s

Mendel conducted experiments with pea plants to investigate the inheritance patterns of different features.

Mendel's experiment

• Mendel cross-pollinated tall pea plants with short pea plants.

• The offspring of the parent plants were all tall, none were short.

• Mendel allowed the first generation of offspring plants to self-pollinate.

• Some of the second generation offspring plants were short.

• on average, for every three tall plants, there was one short plant.

Mendel repeated the experiment studying other traits

such as flower colour, seed colour and pod shape.

In these experiments he observed similar patterns, he concluded that

• Inherited traits are controlled by factors (now known as genes)

• Individuals have two copies of each factor.

history of genetics

• In 1869, Friedrich Miescher first isolated the substance which we now know as DNA.

• In the 1940’s, scientists discovered that DNA is responsible for inherited characteristics

• By the mid 1950’s, the structure of DNA was determined – it looks like a twisted ladder, called a helix.

DNA is called

Deoxyribonucleic acid

DNA is found in

the nucleus of cells

DNA contains

the genetic code for every structure and function in an organism.

DNA also determines

the inherited characteristics of an organism.

DNA in a person is

unique

Your DNA is

a unique of combination of genetic material passed down from both of your parents

Is it possible for two people to have the same DNA

- Yes.

•Identical twins.

•Same cell, contains same DNA.

•Divides so each have same DNA

DNA is made of

of smaller molecules called nucleotides

Nucleotide molecules have three main parts:

‐A Phosphate group

‐A Deoxyribose sugar

‐A Nitrogenous base

The nucleotides are arranged in a spiral, ladder like structure, called a

helix

sides of the ladder are made of

alternating sugar and phosphate

steps of the ladder

nitrogenous bases

in DNA there are 4 nitrogenous bases

• Adenine A

• Thymine T

• Guanine G

• Cytosine C

each nitrogenous base will only bond with

one other specific base

• known as a complementary base pair

complementary base pairs

• Adenine and Thymine

• Cytosine and Guanine

all the cells in your body except red blood cells have

a nucleus that contains DNA

The DNA is identical in each cell which means that

it must be possible to copy DNA molecules perfectly

DNA replication is the process by which

DNA makes a copy of itself

• this occurs just before the cell divides into 2 new cells

• DNA replication occurs in stages

Stage 1: straightening and separation

• the double helix untwists

• an enzyme separates the individual strands of the double helix

• This exposes the nitrogenous bases

  

Stage 2: constructing copies

• within the nucleus there are free nucleotides which are not part of a DNA chain

• The free nucleotides connect to the exposed nitrogenous bases following complementary base pairing rules (A with T and C with G).

• This forms two strands of DNA which are both identical to the original.

  

Stage 3: Checking for mistakes

•The replication process is now complete, with two identical double helixes being formed. 

•The two new DNA strands are “proofread” by enzymes.

•Any errors in base sequencing are corrected