Mod 5 HEREDITY: DNA and Polypeptide synthesis Flashcards
Outline the differences between prokaryotic and eukaryotic DNA
Prokaryotic DNA is:
- Not bound to any proteins, hence does not form chromatin
- No introns present, hence genomes are compacts
- Contains plasmids
- Instead of a nucleus, there is a nucleoid where DNA is able to freely float
Eukaryotic DNA:
- Is held within the nucleus
- Bound to histone proteins
- Contains large amount of introns
- Does not contain plasmids except some organelles (i.e., mitochondria and chloroplast)
- Linear structure
How is prokaryotic DNA packaged?
Packaged via nucleoid-associated proteins that are responsible for making the DNA in a loop-form structure
How is eukaryotic DNA packaged?
Packaged via histone proteins, giving them their linear structure
Identify the quantity of prokaryotic DNA
Typically, contains one chromosome that have few copies of it, having plasmids and base pair ranges of 100k - 20 million
Identify the quantity of eukaryotic DNA
Contains multiple chromosomes with no plasmids, and base pair range could reach billions.
Identify the replication of prokaryotic DNA
Prokaryotes can replicate their DNA fast, of 2000 base pairs per second, 1 replication fork
Identify the replication of eukaryotic DNA
Eukaryotic cells replicate their DNA slow, of about 100 base pairs per second, with multiple replication forks
Identify the information content of prokaryotic DNA
Prokaryotic cells are organised in operons; they code for a variety of proteins. One version of each gene is present.
Identify the information content of eukaryotic DNA
Eukaryotic cells are organised in genes that encode for a specific protein. Consist of two versions of each gene, one from each parent.
Define polypeptide
Many peptide bonds connecting to the many amino acid chains
Define protein
A functioning complex composed of one or more polypeptides
Define amino acids
Building blocks of proteins, determined by a nucleotide sequence
Outline the two stages of polypeptide synthesis
Transcription and translation
Describe the process of transcription
Transcription is the first step of polypeptide (protein) synthesis, in which a messenger RNA (mRNA) is created via a stand of DNA as a template. DNA unwinds and unzips, with one strand being copied to create a complementary mRNA molecule. This is catalysed with the help of RNA polymerase, an enzyme responsible for the adding of complementary base pairs. All of this occurring in the cell nucleus of the cell, readying to be sent out of the nucleus into the cytoplasm for the next stage.
Describe the process of translation
Translation follows transcription, in which it is responsible for translating the mRNA into an amino acid sequence. This is done with the help of tRNA (transfer). tRNA is responsible for matching the amino acid of the mRNA codon via complementary anticodon. All of this occurs in the cytoplasm of the cell.
True or False: In the synthesis of polypeptides, adenine pairs with uracil in the DNA strand being transcribed.
False. In polypeptide synthesis, adenine pairs with uracil in the mRNA strand being transcribed from the DNA, not within the DNA strand itself.
Outline the differences between mRNA and tRNA
mRNA provides the sequence of codons that determine the order of amino acids in the protein, where tRNA matches its anticodon with the codon on the mRNA to add the correct amino acid to the growing polypeptide chain
mRNA generally has a short lifespan, quickly degraded after translation to prevent unnecessary protein production. tRNA is more stable, and can be reused multiple times during translation.
Assess the importance of mRNA and tRNA in transcription and translation
In the transcription and translation process, tRNA and mRNA are incredibly important in the formation of proteins. In transcription, the mRNA strand forms from the template strand DNA, read by RNA polymerase enzyme. Here is then sent from the nucleus to the ribosomes in the cytoplasm. In the absence of mRNA, the sequence of amino acids in DNA codd would not form, meaning that proteins cannot be produced and the organism ceases to exist. In the absence of tRNA, the mRNA sequence will have no way to be converted into amino acids. Consequently, the polypeptide chains would not be formed, leading to no synthesis of proteins that play a vital role in our body.
Analyse the function and importance of polypeptide synthesis
Polypeptide synthesis is the process of assembling amino acids into functioning proteins, comprising of transcription where DNA is converted into mRNA, carrying genetic information from nucleus to cytoplasm, and translation where ribosomes with the help of tRNA, decodes mRNA into polypeptide chains that form the bases of proteins. To code for a functional protein, it requires accurate translation to code for a protein that carries a specific function in the body. For this reason, organisms are able to produce necessary functional proteins to sustain life.
Define gene expression
Genes are used in protein synthesis to influence physical characteristics of species.
Define and provide examples of a phenotype
Physical expression of the genotype (I.e., eye and hair colour)
Identify traits that are not influenced by the environment
Blood type
Eye colour
Genetic disorders such as cystic fibrosis
Identify traits that are influenced by the environment
Breast cancer
Schizophrenia
Hypertension
How are constitutive genes and regulated genes expressed?
Constitutive genes are always expressed and not as likely to be influenced by the environment, whereas regulated genes are expressed/silenced depending on environment through epigenetic marks
Recall TWO relevant case studies for environmental influence
Temperature has an effect on reptile gender, affected in the reptile egg incubation temperature during the thermosensitive period. This determines the sex of an offspring, as their gonadal tissue is responsive to the temperature. For instance. European pond turtle have an incubation period of 75–80 days. 25°C = offspring born as males. 28.5°C = eggs will carry as male and female.
30°C = offspring are females
Hydrangea flower colour is determined by the pH of soil. Acidic soils produce blue blooms and alkaline soils produce pink, despite being genetically identical hydrangea. Here highlights the influence of the environment on the phenotypic expression.
Proteins have four types of structure. Identify them.
Primary
Secondary
Tertiary
Quaternary
Describe primary structure
Amino acid sequence that is linear, held by covalent peptide bonds. This forms a peptide chain.
Describe secondary structure
The protein coils and folds due to hydrogen bonds between peptides.
Recall alpha-helix and beta-sheet
They are ways in which proteins are structured under secondary forms. Alpha-helix is when the backbone of the protein coils around a helix axis in clockwise direction.
Beta sheets are when the protein’s backbone is nearly fully extended.
Describe tertiary structure
A three-dimensional folding of the protein, determined by bonds between side chains
Describe quaternary structure
The arrangement of multiple polypeptide subunits, forming a functional protein. Weakened hydrogen bonds that are easily broken by changes in the environment, therefore the protein can lose its structure and becomes denatured.
Identify what fibrous proteins are, providing an example
Molecules made from repetitive amino acid sequences, maintaining the structural integrity and function of various tissues and organs in the body, such as actin, providing assistance in muscle contraction.
Identify what globular proteins are, providing an example
Complex proteins that consist of tertiary/quaternary structure, playing various roles in cellular functions, such as catalysis, transport, regulation, and immune response. For instance, enzymes.
List the type of fibrous protein
Contractile proteins
Define contractile proteins and provide an example
Cell movement and muscle contraction For instance, actin is involved in muscle contraction
List and define the types of globular proteins (THESIS), providing an example of each.
Transport proteins - Transports molecules within the body, such as haemoglobin, assisting in carrying oxygen throughout the body.
Hormonal proteins - Messenger proteins coordinating cellular functions, such as insulin.
Enzymes - Speed up the rate of chemical reactions. For instance, lactase breaks down lactose found in milk.
Structural proteins - Provide support and strength, such as keratin
Immunoglobulins - Defends against pathogens, such as antibodies.
Storage proteins - Store amino acids that are used for growth, such as ferritin, storing iron in the body.
