Biology Exam

• 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.
• In the 1850’s, Mendel conducted experiments with pea plants to investigate the inheritance patterns of different features.
• 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.
• Mendels experiments - pea plants

  A) short and tall plant

  B) generation 1 all tall

  C) generation 2 3:1

  
• Mendel repeated the experiment studying other traits, such as flower colour, seed colour and pod shape.In these experiments he observed similar pattern
• He concluded that:Inherited traits are controlled by factors    (now known as genes) and Individuals have two copies of each factor.
• In 1869, Friedrich Miescher first isolated the substance which we now know as DNA.
• DNA stands for Deoxyribonucleic Acid
• 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 found in the nucleas of cells
• contains genetic code for every structure & function in an organism
• dna determines inherited charachteristics of an organism
• Your DNA is a unique of combination of genetic material passed down from both of your parents
• This can be used in forensics to place people at a crime scene
• The combination of these characteristics influences every aspect of an individual including physical, emotional, social and cognitive characteristics.
• •DNA is made of smaller molecules called nucleotides, Nucleotide molecules have three main parts:‐A Phosphate group‐A Deoxyribose sugar ‐A Nitrogenous base
• structure of a double helix ladder

  A) deoxyribose sugar

  B) phosphate group

  C) nitrogenous bases

  
• complementary base pairs (nitrogenous base pairs) : Adenine & thymine, cysotine and guanine
• All the cells in your body, except red blood cells, have a nucleus that contains DNA.
• Stage 1: Straightening and Separation

  The double helix untwists. An enzyme separates the individual strands of the double helix (like unzipping a zipper). This exposes the nitrogenous bases.
• Stage one: straightening and seperation

  A) double helix structure unwinds

  B) Nitrogenous bases are exposed

  C) Enzyme seperates 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
• Step 3: Checking for Mistakes

  A) two identical double helix are formed

  
• Within the nucleus of a cell, the DNA is loosely packaged similar to wool, so that it can be easily accessed. This form of DNA is called chromatin
• When a cell prepares to reproduce, the DNA condenses into a tight package known as a chromosome. At this point the chromosomes are visible  within the nucleus
• Cell may contain one or two copies of the genetic material depending where they are in their life cycle. One copy = single stranded chromosome.Two copies = double stranded chromosome
• Each individual copy of the genetic material within a chromosome is called a chromatid. Single stranded chromosome has one chromatid. Double stranded chromosome has two chromatids
• Two chromatids join in the middle at a point called the centromere and can be referred to as sister chromatids
• Small sections of DNA are called genes. Genes determine the characteristics of an organism. The different order in which the nitrogenous bases are arranged within a gene are what gives an individual their unique characteristics
• Most cells within the human body contain 46 chromosomes•23 come from the father, 23 from the mother. All 46 chromosomes in a human are organised into pairs, known as homologous pairs
• A pictorial representation of all of the chromosomes in a         cell  is called a karyotype.It shows the chromosomes in homologous pairs 
• The first 22 pairs of chromosomes are called autosomes and determine the general characteristics and function of an organism
• The last two chromosome are called sex chromosomes and determine the gender of the individual•X X = female     and   X Y = male
• STEP TWO - CONSTRUCTING COPIES : FREE NUCLEOTIDES CONNECT TO EXPOSED NITROGENOUS BASES, FORMS TWO STRANDS OF DNA
• DNA stands for Deoxyribonucleic Acid.•
• Nucleotides are made up of: A phosphate group, A deoxyribose sugar, A nitrogenous base
• There are four types of nucleotide bases found in DNA: adenine (A), thymine (T), cytosine (C) and guanine (G)