DNA And Inheritance Flashcards
(22 cards)
Cell Theory
- All living things are composed of one or more cells
- The cell is the smallest form of life
- All cells come from pre-existing cells, via cell division
All Cells Have Regardless
Cell membrane - acts like the ‘skin’, forming a barrier around the cell and controlling the entry and exit of wastes and nutrients
Cytoplasm - the jelly-like fluid inside/within the cell membrane that surrounds everything inside the cell
DNA (deoxyribonucleic acid) - the genetic information that contains instructions for making the proteins your body needs to keep you alive
Ribosomes - synthesis proteins from amino acids, protein is needed cell growth, repair and general cell function
Unicellular Vs Multicellular
Unicellular – life forms consist of only one cell e.g - bacteria
Multicellular – life forms are made of many cells e.g - humans, animals, plants
Types Of Cells
Eukaryotic-
- More complex, evolved from prokaryotes
- Membrane bound organelles
- Contain a nucleus which stores the DNA
- Usually multi-cellular
- They can be found in plants, animals and fungi
Prokaryotic-
- Evolutionarily ancient (3.8 billion years ago)
- No membrane bound organelles
- No nucleus – DNA is free in the cytoplasm
- Unicellular
- E.g - bacteria and
archaea
Cell Nucleus
- Control centre/dictator of the cell
- Contains DNA (Eukaryotic only)
- Usually, the easiest organelle to see under a microscope
- Usually, one per cell
DNA Structure
DNA is arranged in a double helix; that is, two strands of DNA are twisted together resembling a long, spiralling string
(It’s made up of a sugar phosphate backbone and four nucleotide bases: adenine, guanine, cytosine, and thymine (they hold the two strands together))
DNA is said to be a polymer made of many smaller monomers called nucleotides. A nucleotide is one nitrogen base, one ribose sugar and one phosphate
Genes
- Are sections of DNA
- Some genes may dictate your eye colour, others your hair colour, and others your blood type.
- To do this, most genes will code for proteins, and then those proteins will do various jobs around the body
Chromosomes
A string of DNA can be wound up, or condensed, into structures called chromosomes
One chromosome is made from a single, long string of DNA
If DNA is yarn, then chromosomes are like balls of yarn, used to organize the DNA
Most human cells contain a full set of the bodies genetic information. A total of 23 pairs of chromosomes in every cell nucleus
Chromosome Structure Facts
One feature that is the same for all species is that chromosomes consist of one pair of chromatids.
So the “X” shape that they make is two chromatids joined together to form a chromosome
Chromosome Structure (Mental) Diagram
Two Identical Chromatids-
One is the exact copy of the other and each contain one DNA molecule
P Arm-
Short arm structure
Centromere-
Constricted point of the chromosome
Q Arm-
Long arm structure
DNA Molecule-
Long string like DNA molecule formed into compact structure by proteins called histones
What Are Mutations?
A mutation is a change in the genetic material of an organism, usually in the DNA
Mutations can be random and the result of chance or from the exposure to mutagens
Mutations in the genetic code are usually permanent
They can have harmful effects (cause disease) and in some cases, beneficial ones.
E.g - some bacteria develop mutations that make them antibiotic resistant
Mutations Can Be Caused By
Errors in DNA replication - (DNA is copied to make new cells, mistakes can happen during this process
Cell divisions - (errors during mitosis and meiosis, the process of making new cells)
Mutagens - (physical, chemical or biological factors such as radiation exposure or smoking)
Types Of Mutations
Spontaneous - occur when there are random mistakes in the normal process of DNA replication, such as strand slippage
Induced - are caused by the environment, such as the impact of radiation or certain chemicals
Gene Mutations
Point-
Point mutations involve changes to the bases in a DNA molecule (occur within a gene)
Remember, the DNA codes for amino acids which make proteins
If a base is substituted and the amino acid is not changed, a silent mutation occurs
If the amino acid is altered, the final protein product will be altered and could cause disease
Frameshift-
Is caused by an insertion or deletion leading all the amino acids after this point to be changed
Frameshift mutations drastically change the kinds of amino acids that will be produced, and can drastically change the resulting protein
Mitosis
- Is the process of somatic cells, dividing into two identical cells
- Eukaryotes need new cells for growth, renewal and repair.
- DNA in the cell is replicated before mitosis so each new daughter cell gets a copy
Meiosis
- Is the process of gamete (sex cell) formation: sperm and eggs
- A parent cell will still replicate it’s DNA, however, the cell divides twice, to make 4 gametes, each with only half of the amount of DNA than a somatic cell
Meiosis Phases
Interphase - cell grows and replicates DNA
Prophase I - chromosomes condense/come together to form tetrads
Metaphase I - tetrads line up in the middle and spindle fibres attach
Anaphase I - Chromosomes seperate and are pulled to opposite ends
Telophase I - The cell begins to divide and a new nucleus forms around the chromosomes (cleavage) (not fully separated)
Cytokinesis - separates/divides cytoplasm (cell fully separates) and forms two Diploid daughter cells
Process than repeats again except the result is four Haploid daughter cells
Heredity
The passing on of genes or genetic information from parents to their offspring
Environment
Is the set of external factors that have acted on a person throughout their life
Alleles
Are variations of a gene
They code for different versions of the same characteristic
Genotype Vs Phenotype
Person’s alleles make up their genotype
The trait these alleles result in are called their phenotype
Homozygous Vs Heterozygous
Homo-
If a person carries two of the same alleles
Hetero-
If a person carries one of each type of allele for a particular trait
Examples-
Homo Dominant = HH (the dominant allele overrules the recessive one)
Homo Recessive = hh (trait that tends to be masked by other inherited traits)
Hetero = Hh
