UBC Biol 111 Midterm 1

With Lynn Norman as the professor!

7 characteristics of life

1. Composed of one or more living cells

2. Possess DNA

3. Can grow and develop

4. Can reproduce

5. Sense and react to environment change

6. Have a metabolism that convert food energy or solar energy into ATP

7. Maintain internal homeostasis

Cells

Smallest building blocks of life

Unicellular

Only has one cell, including bacteria, archaea, protozoans, and yeast

Structural features of cells

1. Cell membrane

2. Cytoplasm

3. Ribosomes

4. DNA

Cell membrane

Semipermeable that encloses the cell and acts as a barrier between the cell’s internal and external environment

Cytoplasm

The liquid component of a cell plus the floaty bits. Analogy: bubble tea.

Ribosomes

Tiny structures that carry out protein synthesis

DNA

A molecle that carries genetic instructions for the development and functioning of a cell

Prokaryote cell

No nucleus, single, circular chromosome, no membrane bound organells

Eukaryote cell

Has nucleus, linear chromosomes with more than one chromosomes, has membrane-bound organells like the mitochondria

Organelles

Subcellular structures that perform a specific function or functions, including nucleus, mitochondria, and chloroplasts 

Nucleus

Stores genetic information for a cell

Mitochondria

Produces ATP for the cell

Chloroplasts

Found in plants and algae - site of photosynthesis, where light energy is converted into sugars

Ribosomes

Responsible for protein synthesis

Endosymbiosis

Explains how membrane-bound organells such as the mitochondria and the chloroplast arose when one bacterium engulfed another bacterium and they share a mutual beneficial symbiotic relationship

Evidence for endosymbiosis

1. Circular DNA: both mitochondria and chloroplasts have their own circular DNA like in prokaryotes

2. Double membranes: mitochondria and chloroplasts are surrounded by two separate membranes

3. Reproduction: Mitochondria and chloroplasts reproduce by pinching in half

4. Genes: Mitochondria and chloroplasts have their own DNA similar to genes found in prokaryotes

Genetics

The study of genes, genetic variation and heredity, how genetic traits/conditions are passed from one generation to the next

Importance of genetics

1. Know causes of diseases

2. Determine who is at greater risk for diseases

3. DNA evidence to convict crminals

4. Wildlife preservation

5. Joy of discovery

DNA

A double-stranded polunucleotides that coil around each other molecule that looks like a 3D spiral staircase. Primary function is to store the genetic recipes for all the proteins that make up an organism.

Nucleotide

Contains a sugar group, phosphate group, and one of the 4 types of nitrogenous bases

Genome

The entire set of DNA found in a cell/organism, measured as the number of base-pairs in the DNA

Chromosomes

Humans have a total of 46. Contains the centromere, arm, and telomere. To form this, DNA is wrapped around histone proteins.

Genes

Small sections of DNA that code for a specific protein. Basic unit of inheritance. Traits are passed from parents to children in the form of this.

Thenotype

Genes in combination with the environment. Observable physical properties of an organism, could be morphological, physiological, behavioural, may be qualitative or quantitative.

Alleles

Different versions of the same gene. Responsible for variation in inherited traits. Arise due to mutations in the DNA. Same gene of this are separated by a “/”

Mutation

A change in the sequence of nucleotides in the DNA. May be as small as a change in one nucleotide. Caused by mistakes when DNA is replicating, environmental factors. Change in nucleotide sequence can change the amino acid sequence and function of the protein.

Transcription

First step to get from a gene to the protein. Include “unzipping” the DNA. One strand serves as a template for the synthesis of a single mRNA strand with the help of enzymes.

Translation

Second step from a gene to the protein. Include reading the mRNA molecule in 3-letter blocks andeach produces a specific amino acid. Amino acids join together to form a protein.

Substitution

A type of mutation where the nucleotide has beenchanged

Insertion

A type of mutation where a new nucleotide is added

Deletion

A type of mutation where a nucleotide has been removed

Ploidy

Number of sets of chromosomes in a cell

Haploid

Number of different types of chromosomes present in a cell or in one set. 1 of each chromosome type or one complete set of chromosomes. These are also gametes.

Somatic cells

Any cells other than gametes

Diploid

2 of each chromosome, or 2 complete sets of chromosomes

Polyploid

3 or more of each chromsome, or 3 or more complete sets of chromosomes

Sex chromosomes

Chromosomes that carry alleles that determine an individual’s biological sex

Karyotype

A visual depcition of the chromosomes in a cell

Haploid number

Determine the haploid number using the equation that describes chromosomes in a nucleus. 2n = 46, where 2 refers to the ploidy, n to the haploid number, and 46 and total number of chromosomes in a somatic cell.

Distinguish different chromosomes

1. Differences in size, human autosomes labelled 1-22, with #1 the longest

2. Differences in centromere location

Centromere

The constriction point on a chromosome, attachment site for kinetochore protein patches and spindle fibers during cell division. Divides the chromosomes into two arms.

Homologous chromosomes

Matched pair of chromosomes, one from each parent. Same size, same centromere location, same sequence of genes, different alleles.

Unreplicated chromosome

Drawn with a line and a dot in the middle

Replicated chromosome

Drawn with 2 DNA molecules joined at a single centromere

Sister chromatid

Replicated DNA has two. Each is one DNA molecule and both are attached to the centromere = 1 chromosome. If asked how many chromosomes are present in a cell, count the number of centromeres.

Locus

Genes have a specific fixed location on a particular chromosome

Genotype

The set of alleles/genes carried by an individual or a cell that relate to specific trait that we are interested in

Heterozygous

Carries two different alleles of the same gene

Genotype notation

Alleles of the same gene separated by a “/”, different genes separated by a “;”

Mitosis & meiosis

Nuclear divisions

Cytokinesis

Division of cytoplasm

Mitosis

Occurs in somatic cells. Goal is for the parent cells to produce two progeny/daughter cells that are genetically identical to the parent cell and each other.

Cell cycle

Contains

1. G1

2. S/DNA synthesis

3. G2

4. Mitosis

5. Cytokinesis

Interphase

Includes the G1, S, and G2. Longest part of the cell’s life.

G1

The cell is performing its functions and DNA is Not replicated

Go phase

A phase for non-dividing cells where it never replicates and it just works indefinitely

Gap 1 phase

When a cell receives signal to start dividing, prepare in G1 by:

• growing

• duplicating organelles

• accumulating nucleotides

• obtains energy reserves

G1 checkpoint

At the end of G1 to check for sufficient number of organelles, cell size, and if DNA is damaged

S phase of interphase

When the DNA replicates and sister chromatids are formed

G2 Phase or Gap phase 2

Shortest part of interphase where final preparations are made before cell divides

G2 checkpoint

At the end of G2 to check if DNA are replicated and DNA is undamaged

M phase

Mitosis & cytokinesis

Mitosis

Divided into 4 or 5 PPMAT phases

1. prophase

2. prometaphase

3. metaphase

4. anaphase

5. telophase

Prophase

First phase of mitosis. Chromosomes condense, and spindle apparatus begins to form.

Prometaphase

Second phase of mitosis. Nuclear envelope breaks down. Microtules contact chromosomes at kinetochores.

Metaphase

Third phase of mitosis. Chromosomes complete migration to middle of cell or the imaginary plane equidistant from two poles of cell

Anaphase

Fourth step of mitosis. Spindle fibres pull sister chromatids (now chromosomes) to opposite poles of the cell

Telophase

Fifth step of mitosis. Spindle fibres breaks down, nuclear envelope develope, and chromosome decondense

Cytokinesis

Last step of mitosis. Plasma membrane pinch in to create progeny.

M checkpoint

Final checkpoint near the end of metaphase to see if spindle fibers are firmly attached to all sister chromatids

Meiosis

A type of cell division found in sexually reproducing organisms. Goal is for a diploid parent cell to produce 4 genetically distinct haploid daughter cells or gametes. Occurs in germ cells in the gonads to produce gametes.

Meiosis I

The homologous chromosomes separate from each other

Meiosis II

Sister chromatids separate from each other

Interphase of meiosis

The germline cells goes through G1, S, G2 to replicate DNA and cell checked to make sure it is ready to divide

Early prophase I

The chromosomes condense, nuclear membrane disassembles and homologous chromosomes come together called synapsis

Synapsis

Homologous chromosomes become tightly associated along their lengths in a structure called a tetrad

Tetrad

4 chromatids used for synapsis

Late prophase I

Where non-sister chromatids exchange bits of DNA in a process called crossing-over. Outcome is called recombination. 

Chiasma

The contact points between non-sister chromatids of homologous chromosomes. The sites of DNA breakage by specialized enzymes

Crossing-over

Specialized proteins deliberately break the DNA molecules at the same location in 2 non-sister chromatids of homologous chromosomes. Rather than joining broken segment back, the broken segment is joined to the chromatid of the other homolog. Results in the exchange of genetic material between non-sister chromatids, and sister chromatids are no longer genetically identical.

Metaphase I

Homologs align opposite each other on either side of the metaphase plate. Indepedent assortment of homologous chromosomes occur.

Independent assortment of homologous chromosomes

The 2nd source of genetic variation during meiosis, where the alignment of chromosome 1 homologs is independent of the alignment of chromosome 2 homologs.

Anaphase I

The spindle fibers contract and the homologous chromosomes separate. They move towards poles.

Telophase I & Cytokinesis I

Nuclear envelope may reform and cytokinesis creates two haploid cells. Sister chromatids still attached at centromere.

Interkinesis

At the end of Meiosis I, no interphase for cells. This is where spindle fibres disintegrate.

Meiosis II

Sister chromatids seprate similar to mitosis but cell is haploid.

Linked genes

Genes located close together on the same chromosome, so they will travel together into a gamete unless crossing-over and recombination occurs.

2^n

Equation used to calculate the number of possible gamete genotypes that could be produced if genes are not linked or they are linkedwith crossing over. N = number of genes that are heterozygous.

Trait

An observable characteristic of an organism at any level. Ex: skin colour, skin roughness, body length, sex, heart beat rate

Phenotype

The state of the trait. Specifies and sometimes have a numerical value to the trait. Ex: golden eye colour, rough skin, body length is short. Determined by the interaction between genotype and environment.

Dominant allele

Produces the dominant phenotype in individuals who have at least one copy of the allele. Can come from either parent.

Recessive allele

Produces a recessive phenotype only if an individual has two copies of the allele.

Carriers

An individual who carries one dominant allele and one recessive allele will have the dominant phenotype. They are also:

Non-dominance

Includes incomplete dominance and co-dominance. Can result in 3 possible genotypes and 3 different phenotypes.

Incomplete dominance

An allelic relationship where one allele is not diminant over the other allele. The phenotype of the heterozygous tends to be intermediate between the phenotypes of the homozygotes.

Co-dominance

Allelic relationship whic hthe heterozygote exhibits the phenotype of both alleles at the same time.

Punnett square

A matrix/square grid that can be used to predict the possible genotypes and penotypes of offspring from a particular cross. Assumes random fusion of eggs and sperm,

Test cross

Crossing an individual with the dominant phenotype and unknown genotype with a homozygous recessive. The phenotypes of the offspring are examined.

True-breeding / Pure-breeding

Describe an individual that is homozygous for a gene